Add 'xo-websock/' from commit '57bf06a68f'

git-subtree-dir: xo-websock git-subtree-mainline: 97eefaea22 git-subtree-split: 57bf06a68f
2025-05-11 15:08:51 -05:00 · 2025-05-11 15:08:51 -05:00 · dd1a6b1afc
commit dd1a6b1afc
parent 97eefaea22 57bf06a68f
30 changed files with 4667 additions and 0 deletions
--- a/xo-websock/.github/workflows/main.yml
+++ b/xo-websock/.github/workflows/main.yml
@ -0,0 +1,261 @@
+name: build xo-callback + xo dependencies
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+env:
+  # Customize the CMake build type here (Release, Debug, RelWithDebInfo, etc.)
+  BUILD_TYPE: Release
+
+jobs:
+  build:
+    # The CMake configure and build commands are platform agnostic and should work equally well on Windows or Mac.
+    # You can convert this to a matrix build if you need cross-platform coverage.
+    # See: https://docs.github.com/en/free-pro-team@latest/actions/learn-github-actions/managing-complex-workflows#using-a-build-matrix
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: checkout source
+      uses: actions/checkout@v3
+
+    - name: Install catch2
+      # install catch2.  see [[https://stackoverflow.com/questions/57982945/how-to-apt-get-install-in-a-github-actions-workflow]]
+      run: sudo apt-get install -y catch2
+
+    - name: Install libjsoncpp (dep of libwebsockets)
+      # install jsoncpp
+      run: sudo apt-get install -y libjsoncpp-dev
+
+    - name: Install libwebsockets
+      # install libwebsockets.
+      run: sudo apt-get install -y libwebsockets-dev
+
+    # ----------------------------------------------------------------
+
+    - name: Clone xo-cmake
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/xo-cmake
+        path: repo/xo-cmake
+
+    - name: Configure xo-cmake
+      run: cmake -B ${{github.workspace}}/build_xo-cmake -DCMAKE_INSTALL_PREFIX=${{github.workspace}}/local repo/xo-cmake
+
+    - name: Build xo-cmake (trivial)
+      run: cmake --build ${{github.workspace}}/build_xo-cmake --config ${{env.BUILD_TYPE}}
+
+    - name: Install xo-cmake
+      run: cmake --install ${{github.workspace}}/build_xo-cmake
+
+    # ----------------------------------------------------------------
+
+    - name: Clone indentlog
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/indentlog
+        path: repo/indentlog
+
+    - name: Configure indentlog
+      # configure cmake for indentlog in dedicated build directory.
+      run: cmake -B ${{github.workspace}}/build_indentlog -DCMAKE_MODULE_PATH=${{github.workspace}}/local/share/cmake -DCMAKE_INSTALL_PREFIX=${{github.workspace}}/local repo/indentlog
+
+    - name: Build indentlog
+      run: cmake --build ${{github.workspace}}/build_indentlog --config ${{env.BUILD_TYPE}}
+
+    - name: Install indentlog
+      # install into ${{github.workspace}}/local
+      run: cmake --install ${{github.workspace}}/build_indentlog
+
+    # ----------------------------------------------------------------
+
+    - name: Clone refcnt
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/refcnt
+        path: repo/refcnt
+
+    - name: Configure refcnt
+      # configure cmake for refcnt in dedicated build directory.
+      run: cmake -B ${{github.workspace}}/build_refcnt -DCMAKE_MODULE_PATH=${{github.workspace}}/local/share/cmake -DCMAKE_PREFIX_PATH=${{github.workspace}}/local -DCMAKE_INSTALL_PREFIX=${{github.workspace}}/local repo/refcnt
+
+    - name: Build refcnt
+      run: cmake --build ${{github.workspace}}/build_refcnt --config ${{env.BUILD_TYPE}}
+
+    - name: Install refcnt
+      # install into ${{github.workspace}}/local
+      run: cmake --install ${{github.workspace}}/build_refcnt
+
+    # ----------------------------------------------------------------
+
+    - name: Clone subsys
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/subsys
+        path: repo/subsys
+
+    - name: Configure subsys
+      # configure cmake for subsys in dedicated build directory.
+      run: cmake -B ${{github.workspace}}/build_subsys -DCMAKE_MODULE_PATH=${{github.workspace}}/local/share/cmake -DCMAKE_PREFIX_PATH=${{github.workspace}}/local -DCMAKE_INSTALL_PREFIX=${{github.workspace}}/local repo/subsys
+
+    - name: Build subsys
+      run: cmake --build ${{github.workspace}}/build_subsys --config ${{env.BUILD_TYPE}}
+
+    - name: Install subsys
+      # install into ${{github.workspace}}/local
+      run: cmake --install ${{github.workspace}}/build_subsys
+
+    # ----------------------------------------------------------------
+
+    - name: Clone reflect
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/reflect
+        path: repo/reflect
+
+    - name: Configure reflect
+      # configure cmake for reflect in dedicated build directory.
+      run: cmake -B ${{github.workspace}}/build_reflect -DCMAKE_MODULE_PATH=${{github.workspace}}/local/share/cmake -DCMAKE_PREFIX_PATH=${{github.workspace}}/local -DCMAKE_INSTALL_PREFIX=${{github.workspace}}/local repo/reflect
+
+    - name: Build reflect
+      run: cmake --build ${{github.workspace}}/build_reflect --config ${{env.BUILD_TYPE}}
+
+    - name: Install reflect
+      # install into ${{github.workspace}}/local
+      run: cmake --install ${{github.workspace}}/build_reflect
+
+    # ----------------------------------------------------------------
+
+    - name: Clone callback
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/xo-callback
+        path: repo/callback
+
+    - name: Configure callback
+      # configure cmake for callback in dedicated build directory.
+      run: cmake -B ${{github.workspace}}/build_callback -DCMAKE_MODULE_PATH=${{github.workspace}}/local/share/cmake -DCMAKE_PREFIX_PATH=${{github.workspace}}/local -DCMAKE_INSTALL_PREFIX=${{github.workspace}}/local repo/callback
+
+    - name: Build callback
+      run: cmake --build ${{github.workspace}}/build_callback --config ${{env.BUILD_TYPE}}
+
+    - name: Install callback
+      # install into ${{github.workspace}}/local
+      run: cmake --install ${{github.workspace}}/build_callback
+
+    # ----------------------------------------------------------------
+
+    - name: Clone webutil
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/xo-webutil
+        path: repo/webutil
+
+    - name: Configure webutil
+      # configure cmake for webutil in dedicated build directory.
+      run: cmake -B ${{github.workspace}}/build_webutil -DCMAKE_MODULE_PATH=${{github.workspace}}/local/share/cmake -DCMAKE_PREFIX_PATH=${{github.workspace}}/local -DCMAKE_INSTALL_PREFIX=${{github.workspace}}/local repo/webutil
+
+    - name: Build webutil
+      run: cmake --build ${{github.workspace}}/build_webutil --config ${{env.BUILD_TYPE}}
+
+    - name: Install webutil
+      # install into ${{github.workspace}}/local
+      run: cmake --install ${{github.workspace}}/build_webutil
+
+    # ----------------------------------------------------------------
+
+    - name: Clone printjson
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/xo-printjson
+        path: repo/printjson
+
+    - name: Configure printjson
+      # configure cmake for printjson in dedicated build directory.
+      run: cmake -B ${{github.workspace}}/build_printjson -DCMAKE_MODULE_PATH=${{github.workspace}}/local/share/cmake -DCMAKE_PREFIX_PATH=${{github.workspace}}/local -DCMAKE_INSTALL_PREFIX=${{github.workspace}}/local repo/printjson
+
+    - name: Build printjson
+      run: cmake --build ${{github.workspace}}/build_printjson --config ${{env.BUILD_TYPE}}
+
+    - name: Install printjson
+      # install into ${{github.workspace}}/local
+      run: cmake --install ${{github.workspace}}/build_printjson
+
+    # ----------------------------------------------------------------
+
+    - name: Clone randomgen
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/randomgen
+        path: repo/randomgen
+
+    - name: Configure randomgen
+      # configure cmake for randomgen in dedicated build directory.
+      run: cmake -B ${{github.workspace}}/build_randomgen -DCMAKE_MODULE_PATH=${{github.workspace}}/local/share/cmake -DCMAKE_PREFIX_PATH=${{github.workspace}}/local -DCMAKE_INSTALL_PREFIX=${{github.workspace}}/local repo/randomgen
+
+    - name: Build randomgen
+      run: cmake --build ${{github.workspace}}/build_randomgen --config ${{env.BUILD_TYPE}}
+
+    - name: Install randomgen
+      # install into ${{github.workspace}}/local
+      run: cmake --install ${{github.workspace}}/build_randomgen
+
+    # ----------------------------------------------------------------
+
+    - name: Clone ordinaltree
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/xo-ordinaltree
+        path: repo/ordinaltree
+
+    - name: Configure ordinaltree
+      # configure cmake for ordinaltree in dedicated build directory.
+      run: cmake -B ${{github.workspace}}/build_ordinaltree -DCMAKE_MODULE_PATH=${{github.workspace}}/local/share/cmake -DCMAKE_PREFIX_PATH=${{github.workspace}}/local -DCMAKE_INSTALL_PREFIX=${{github.workspace}}/local repo/ordinaltree
+
+    - name: Build ordinaltree
+      run: cmake --build ${{github.workspace}}/build_ordinaltree --config ${{env.BUILD_TYPE}}
+
+    - name: Install ordinaltree
+      # install into ${{github.workspace}}/local
+      run: cmake --install ${{github.workspace}}/build_ordinaltree
+
+    # ----------------------------------------------------------------
+
+    - name: Clone reactor
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/xo-reactor
+        path: repo/reactor
+
+    - name: Configure reactor
+      # configure cmake for reactor in dedicated build directory.
+      run: cmake -B ${{github.workspace}}/build_reactor -DCMAKE_MODULE_PATH=${{github.workspace}}/local/share/cmake -DCMAKE_PREFIX_PATH=${{github.workspace}}/local -DCMAKE_INSTALL_PREFIX=${{github.workspace}}/local repo/reactor
+
+    - name: Build reactor
+      run: cmake --build ${{github.workspace}}/build_reactor --config ${{env.BUILD_TYPE}}
+
+    - name: Install reactor
+      # install into ${{github.workspace}}/local
+      run: cmake --install ${{github.workspace}}/build_reactor
+
+    # ----------------------------------------------------------------
+
+    - name: check cmake-supporting packages
+      run: ls /usr/lib/x86_64-linux-gnu/cmake
+
+    - name: Configure self (websock)
+      # Configure CMake in a 'build' subdirectory. `CMAKE_BUILD_TYPE` is only required if you are using a single-configuration generator such as make.
+      # See https://cmake.org/cmake/help/latest/variable/CMAKE_BUILD_TYPE.html?highlight=cmake_build_type
+      run: cmake -B ${{github.workspace}}/build_websock -DCMAKE_MODULE_PATH=${{github.workspace}}/local/share/cmake "-DCMAKE_PREFIX_PATH=${{github.workspace}}/local;/usr/lib/x86_64-linux-gnu/cmake" -DCMAKE_INSTALL_PREFIX=${{github.workspace}}/local -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}}
+
+    - name: Build self (websock)
+      # Build your program with the given configuration
+      run: cmake --build ${{github.workspace}}/build_websock --config ${{env.BUILD_TYPE}}
+
+    - name: Test self (websock)
+      working-directory: ${{github.workspace}}/build_websock
+      # Execute tests defined by the CMake configuration.
+      # See https://cmake.org/cmake/help/latest/manual/ctest.1.html for more detail
+      run: ctest -C ${{env.BUILD_TYPE}}
--- a/xo-websock/.gitignore
+++ b/xo-websock/.gitignore
@ -0,0 +1,6 @@
+# clangd working space (see emacs+lsp)
+.cache
+# typical cmake build directory (source-tree-nephew)
+.build*
+# symlink to builddir/compile_commands.json;  should be set manually in dev sandbox
+compile_commands.json
--- a/xo-websock/CMakeLists.txt
+++ b/xo-websock/CMakeLists.txt
@ -0,0 +1,30 @@
+# xo-websock/CMakeLists.txt
+
+cmake_minimum_required(VERSION 3.10)
+
+project(websock VERSION 1.0)
+
+include(GNUInstallDirs)
+include(cmake/xo-bootstrap-macros.cmake)
+
+xo_cxx_toplevel_options3()
+
+# ----------------------------------------------------------------
+# c++ settings
+
+# one-time project-specific c++ flags.  usually empty
+set(PROJECT_CXX_FLAGS "")
+#set(PROJECT_CXX_FLAGS "-fconcepts-diagnostics-depth=2")
+add_definitions(${PROJECT_CXX_FLAGS})
+
+# ----------------------------------------------------------------
+
+add_subdirectory(src/websock)
+#add_subdirectory(utest)
+
+# ----------------------------------------------------------------
+# provide find_package() support for websock customers
+
+xo_export_cmake_config(${PROJECT_NAME} ${PROJECT_VERSION} ${PROJECT_NAME}Targets)
+
+# end CMakeLists.txt
--- a/xo-websock/README.md
+++ b/xo-websock/README.md
@ -0,0 +1,55 @@
+# websock library
+
+http library including websocket support.
+Built around the C-library libwebsocket
+
+# dependencies
+
+build+install these first
+
+- xo-somelib [github.com/Rconybea/xo-somelib]
+
+# build + install
+
+## build
+```
+$ cd websock
+$ mkdir build
+$ cd build
+$ INSTALL_PREFIX=/usr/local  # or wherever you prefer
+$ cmake -DCMAKE_MODULE_PATH=${INSTALL_PREFIX}/share/cmake -DCMAKE_PREFIX_PATH=${INSTALL_PREFIX} -DCMAKE_INSTALL_PREFIX=${INSTALL_PREFIX} ..
+$ make
+$ make install
+```
+(also see .github/workflows/main.yml)
+
+## build for unit test coverage
+```
+$ cd xo-websock
+$ mkdir ccov
+$ cd ccov
+$ cmake -DCMAKE_MODULE_PATH=${INSTALL_PREFIX}/share/cmake  -DCMAKE_PREFIX_PATH=${INSTALL_PREFIX} -DCODE_COVERAGE=ON -DCMAKE_BUILD_TYPE=Debug ..
+```
+
+# development
+
+## LSP support
+
+LSP looks for compile commands in the root of the source tree;
+cmake creates them in the root of its build directory.
+
+```
+$ cd xo-websock
+$ ln -s build/compile_commands.json
+```
+
+## display cmake variables
+
+- `-L` list variables
+- `-A` include 'advanced' variables
+- `-H` include help text
+
+```
+$ cd websock/build
+$ cmake -LAH
+```
--- a/xo-websock/cmake/websockConfig.cmake.in
+++ b/xo-websock/cmake/websockConfig.cmake.in
@ -0,0 +1,14 @@
+@PACKAGE_INIT@
+
+include(CMakeFindDependencyMacro)
+
+# note: changes to find_dependency() calls here
+#       must coordinate with xo_dependency() calls
+#       in xo-websock/src/websock/CMakeLists.txt
+#
+find_dependency(reactor)
+find_dependency(webutil)
+find_dependency(Libwebsockets)
+
+include("${CMAKE_CURRENT_LIST_DIR}/@PROJECT_NAME@Targets.cmake")
+check_required_components("@PROJECT_NAME@")
--- a/xo-websock/cmake/xo-bootstrap-macros.cmake
+++ b/xo-websock/cmake/xo-bootstrap-macros.cmake
@ -0,0 +1,35 @@
+# ----------------------------------------------------------------
+# for example:
+#   $ PREFIX=/usr/local   # for example
+#   $ cmake -DCMAKE_MODULE_PATH=prefix -DCMAKE_INSTALL_PREFIX=$PREFIX -B .build
+#
+# will get
+#   CMAKE_MODULE_PATH
+# from xo-cmake-config --cmake-module-path
+#
+# and expect .cmake macros in
+#   CMAKE_MODULE_PATH/xo_macros/xo_cxx.cmake
+# ----------------------------------------------------------------
+
+find_program(XO_CMAKE_CONFIG_EXECUTABLE NAMES xo-cmake-config REQUIRED)
+
+if ("${XO_CMAKE_CONFIG_EXECUTABLE}" STREQUAL "XO_CMAKE_CONFIG_EXECUTABLE-NOT_FOUND")
+    message(FATAL "could not find xo-cmake-config executable")
+endif()
+
+message(STATUS "XO_CMAKE_CONFIG_EXECUTABLE=${XO_CMAKE_CONFIG_EXECUTABLE}")
+
+if (NOT XO_SUBMODULE_BUILD)
+    if (("${CMAKE_MODULE_PATH}" STREQUAL "") OR ("${CMAKE_MODULE_PATH}" STREQUAL prefix))
+        # default to typical install location for xo-project-macros
+        execute_process(COMMAND ${XO_CMAKE_CONFIG_EXECUTABLE} --cmake-module-path OUTPUT_VARIABLE CMAKE_MODULE_PATH)
+        message(STATUS "CMAKE_MODULE_PATH=${CMAKE_MODULE_PATH}")
+    endif()
+endif()
+
+# needs to have been installed somewhere on CMAKE_MODULE_PATH,
+# (e.g. from xo-cmake with the same value for CMAKE_INSTALL_PREFIX)
+#
+include(xo_macros/xo_cxx)
+
+xo_cxx_bootstrap_message()
--- a/xo-websock/include/xo/websock/DynamicEndpoint.hpp
+++ b/xo-websock/include/xo/websock/DynamicEndpoint.hpp
@ -0,0 +1,126 @@
+/* file DynamicEndpoint.hpp
+ *
+ * author: Roland Conybeare, Sep 2022
+ */
+
+#pragma once
+
+#include "EndpointUtil.hpp"
+#include "xo/webutil/HttpEndpointDescr.hpp"
+#include "xo/webutil/StreamEndpointDescr.hpp"
+#include "xo/webutil/Alist.hpp"
+#include <regex>
+
+namespace xo {
+    namespace web {
+        /* a dynamic http endpoint.  content served on-browser-demand
+         * by user-provided callback
+         */
+        class DynamicEndpoint {
+        public:
+            using AbstractSink = xo::reactor::AbstractSink;
+            using CallbackId = fn::CallbackId;
+
+        public:
+            static std::unique_ptr<DynamicEndpoint> make_http(std::string uri_pattern,
+                                                              HttpEndpointFn http_cb) {
+                return (std::unique_ptr<DynamicEndpoint>
+                        (new DynamicEndpoint(std::move(uri_pattern),
+                                             std::move(http_cb),
+                                             nullptr,
+                                             nullptr)));
+            } /*make_http*/
+
+            static std::unique_ptr<DynamicEndpoint> make_stream(std::string uri_pattern,
+                                                                StreamSubscribeFn sub_fn,
+                                                                StreamUnsubscribeFn unsub_fn) {
+                return (std::unique_ptr<DynamicEndpoint>
+                        (new DynamicEndpoint(std::move(uri_pattern),
+                                             nullptr,
+                                             std::move(sub_fn),
+                                             std::move(unsub_fn))));
+            } /*make_stream*/
+
+            std::string stem() const {
+                return EndpointUtil::stem(this->uri_pattern_);
+            } /*stem*/
+
+#ifdef NOT_USING
+            /* true iff incoming_uri matches .uri_pattern */
+            bool is_match(std::string const & incoming_uri) const {
+                /* c++ regex = javascript regexes,
+                 * so these characters are special:
+                 *   ^ $ \ . * + ? ( ) [ ] { } |
+                 */
+            } /*is_match*/
+#endif
+
+            /* get html from this endpoint,  on behalf of uri=incoming_uri;
+             * write html on *p_os
+             *
+             * require: non-null http_fn
+             */
+            void http_response(std::string const & incoming_uri,
+                               std::ostream * p_os) const;
+
+            /* subscribe stream from this endpoint,  on behalf of uri=incoming_uri.
+             * send output to ws_sink
+             */
+            CallbackId subscribe(std::string const & incoming_uri,
+                                 rp<AbstractSink> const & ws_sink) const;
+
+            /* unsubscribe stream from this endpoint;
+             * reverses the effect of a previous call to .subscribe()
+             * that returned id
+             */
+            void unsubscribe(CallbackId id) const;
+
+        private:
+            explicit DynamicEndpoint(std::string uri_pattern,
+                                     HttpEndpointFn http_fn,
+                                     StreamSubscribeFn subscribe_fn,
+                                     StreamUnsubscribeFn unsubscribe_fn);
+
+        private:
+            /* pattern for this endpoint
+             * can be string like
+             *   /fixed/stem/${a}/more/fixed/stuff/${b}
+             * in which case:
+             *
+             * 1. will match uris like:
+             *     /fixed/stem/apple/more/fixed/stuff/bananas
+             *    --> invoke callback with Alist
+             *        ("a" -> "apple", "b" -> "bananas")
+             *    endpoint will be stored in WebserverImpl.stem_map
+             *    under fixed prefix,  in this case
+             *     /fixed/stem/
+             *
+             * 2. will not match uris like:
+             *     /fixed/stem/app/le/more/fixed/stuff/bononos
+             */
+            std::string uri_pattern_;
+            /* regex for matching input that satisfies .uri_pattern:
+             * each occurrence of
+             *    ${...} replaced by [[:alnum:]]+
+             */
+            std::regex uri_regex_;
+            /* variables found in .uri_pattern,
+             * in the order in which they appear
+             * if .uri_pattern is
+             *   /fixed/stem/${a}/more/fixed/stuff/${b}
+             * then .var_v will be:
+             *   ["a", "b"]
+             */
+            std::vector<std::string> var_v_;
+            /* run this function to produce an http response */
+            HttpEndpointFn http_fn_;
+            /* run this function to subscribe event stream */
+            StreamSubscribeFn subscribe_fn_;
+            /* run this function to unsubscribe event stream */
+            StreamUnsubscribeFn unsubscribe_fn_;
+        }; /*DynamicEndpoint*/
+
+    } /*namespace web*/
+} /*namespace xo*/
+
+/* end DynamicEndpoint.hpp */
--- a/xo-websock/include/xo/websock/EndpointUtil.hpp
+++ b/xo-websock/include/xo/websock/EndpointUtil.hpp
@ -0,0 +1,26 @@
+/* file EndpointUtil.hpp
+ *
+ * author: Roland Conybeare, Sep 2022
+ */
+
+#pragma once
+
+#include <string>
+
+namespace xo {
+    namespace web {
+        class EndpointUtil {
+        public:
+            /* find fixed prefix for a URI pattern.
+             * patterns are used with both http endpoints (see DynamicEndpoint),
+             * and stream endpoints (see StreamEndpoint)
+             *
+             * e.g. stem("/dyn/uls/${ulticker}/snap") => "/dyn/uls/"
+             */
+            static std::string stem(std::string const & pattern);
+        }; /*EndpointUtil*/
+
+    } /*namespace web*/
+} /*namespace xo*/
+
+/* end EndpointUtil.hpp */
--- a/xo-websock/include/xo/websock/SafetyToken.hpp
+++ b/xo-websock/include/xo/websock/SafetyToken.hpp
@ -0,0 +1,40 @@
+/* file SafetyToken.hpp
+ *
+ * author: Roland Conybeare, Sep 2022
+ */
+
+#pragma once
+
+namespace xo {
+    namespace web {
+        /* token for cooperative compile-time threadsafety checking.
+         *
+         * requirements for cooperating code:
+         * - token contains no state,  so in principle can be optimized away
+         * - token is deliberately not copyable,  and not moveable
+         * - derive from token, and make derived ctor private
+         * - make method/class responsible for threadsafety a friend of token,
+         *   so it can have exclusive right to create a token instance.
+         * - pass token reference down stack
+         *   to demonstrate ownership of protected resource,
+         *   limited to the lifetime of called function.
+         */
+        template<typename T>
+        class SafetyToken {
+        public:
+            SafetyToken(SafetyToken const & x) = delete;
+            SafetyToken(SafetyToken && x) = delete;
+
+            /* optionally: invoke this to "announce use of a protected resource" */
+            bool verify() const { return true; }
+
+            SafetyToken & operator=(SafetyToken const & x) = delete;
+            SafetyToken & operator=(SafetyToken && x) = delete;
+
+        protected:
+            SafetyToken() = default;
+        }; /*SafetyToken*/
+    } /*namespace web*/
+} /*namespace xo*/
+
+/* end SafetyToken.hpp */
--- a/xo-websock/include/xo/websock/Webserver.hpp
+++ b/xo-websock/include/xo/websock/Webserver.hpp
@ -0,0 +1,116 @@
+/* @file Webserver.hpp */
+
+#pragma once
+
+#include "xo/refcnt/Displayable.hpp"
+#include "xo/printjson/PrintJson.hpp"
+#include "xo/webutil/HttpEndpointDescr.hpp"
+#include "xo/webutil/StreamEndpointDescr.hpp"
+#include <libwebsockets.h>  // temporary,  while moving callbacks
+#include <thread>
+#include <vector>
+#include <memory>
+
+namespace xo {
+    namespace web {
+        enum class Runstate { stopped, stop_requested, running };
+
+        class RunstateUtil {
+        public:
+            static char const * runstate_descr(Runstate x);
+        }; /*RunstateUtil*/
+
+        inline std::ostream & operator<<(std::ostream &os, Runstate x) {
+            os << RunstateUtil::runstate_descr(x);
+            return os;
+        } /*operator<<*/
+
+        class WebserverConfig {
+        public:
+            WebserverConfig() = default;
+            WebserverConfig(std::int32_t port,
+                            bool tls_flag,
+                            bool host_check_flag,
+                            bool use_retry_flag)
+                : port_{port},
+                  tls_flag_{tls_flag},
+                  host_check_flag_{host_check_flag},
+                  use_retry_flag_{use_retry_flag} {}
+
+            std::int32_t port() const { return port_; }
+            bool tls_flag() const { return tls_flag_; }
+            bool host_check_flag() const { return host_check_flag_; }
+            bool use_retry_flag() const { return use_retry_flag_; }
+
+        private:
+            /* accept incoming http requests on this port# */
+            std::int32_t port_ = 0;
+            /* if true,  support https */
+            bool tls_flag_ = false;
+            /* see LWS_SERVER_OPTION_VHOST_UPG_STRICT_HOST_CHECK */
+            bool host_check_flag_ = false;
+            /* see lws_context_creation_info.retry_and_idle_policy */
+            bool use_retry_flag_ = false;
+        }; /*WebserverConfig*/
+
+        /* libwebsocket:
+         * 1. doesn't support multiple threads
+         *    (actually, looks like it does on further examination)
+         * 2. doesn't expose listening ports etc (at least afaik);
+         *    in other words it expects to take over application's main thread
+         *
+         * enforce this property by making webserver a singleton
+         *
+         *    .state      .start_webserver()    .state
+         *   +---------+  -------------------> +---------+
+         *   | stopped |                       | running |
+         *   +---------+                       +---------+
+         *      ^                      |
+         *      |                      | .stop_webserver()
+         *      |                                  |
+         *   +----------------+                    |
+         *   | stop_requested | <------------------/
+         *   +----------------+
+         *
+         */
+        class Webserver : public ref::Displayable {
+        public:
+            using Alist = xo::web::Alist;
+            using PrintJson = xo::json::PrintJson;
+
+        public:
+            /* note: although webserver allows creating multiple instances,
+             *       the underlying libwebsocket library is not advertised to be
+             *       threadsafe
+             */
+            static rp<Webserver> make(WebserverConfig const & ws_config,
+                                      rp<PrintJson> const & pjson);
+
+            /* current state */
+            virtual Runstate state() const = 0;
+            virtual void register_http_endpoint(HttpEndpointDescr const & endpoint) = 0;
+            virtual void register_stream_endpoint(StreamEndpointDescr const & endpoint) = 0;
+
+            /* start thread for this webserver; idempotent */
+            virtual void start_webserver() = 0;
+            /* stop thread for this webserver;  suitable for calling
+             * from interrupt handler
+             */
+            virtual void interrupt_stop_webserver() = 0;
+            /* stop thread for this webserver; idempotent */
+            virtual void stop_webserver() = 0;
+            /* wait until webserver thread stopped */
+            virtual void join_webserver() = 0;
+
+            /* send text to a websocket session identified by session_id */
+            virtual void send_text(uint32_t session_id,
+                                   std::string text) = 0;
+
+            // ----- Inherited from Displayable -----
+
+            virtual void display(std::ostream & os) const;
+        }; /*Webserver*/
+    } /*namespace web*/
+} /*namespace xo*/
+
+/* end Webserver.hpp */
--- a/xo-websock/include/xo/websock/WebsockUtil.hpp
+++ b/xo-websock/include/xo/websock/WebsockUtil.hpp
@ -0,0 +1,18 @@
+/* @file WebsockUtil.hpp */
+
+#pragma once
+
+#include <libwebsockets.h>
+
+namespace xo {
+    namespace web {
+        /* class-as-namespace idiom */
+        class WebsockUtil {
+        public:
+            /* string representation for callback category enum */
+            static char const * ws_callback_reason_descr(lws_callback_reasons x);
+        }; /*WebsockUtil*/
+    } /*namespace web*/
+} /*namespace xo*/
+
+/* end WebsockUtil.hpp */
--- a/xo-websock/include/xo/websock/WebsocketSink.hpp
+++ b/xo-websock/include/xo/websock/WebsocketSink.hpp
@ -0,0 +1,28 @@
+/* file WebsocketSink.hpp
+ *
+ * author: Roland Conybeare, Sep 2022
+ */
+
+#pragma once
+
+#include "xo/reactor/AbstractSink.hpp"
+#include "xo/printjson/PrintJson.hpp"
+
+namespace xo {
+    namespace web {
+        class Webserver;
+
+        class WebsocketSink : public reactor::AbstractSink {
+        public:
+            using PrintJson = xo::json::PrintJson;
+
+        public:
+            static rp<WebsocketSink> make(rp<Webserver> const & websrv,
+                                          rp<PrintJson> const & pjson,
+                                          uint32_t session_id,
+                                          std::string const & stream_name);
+        }; /*WebsocketSink*/
+    } /*namespace web*/
+} /*namespace xo*/
+
+/* end WebsocketSink.hpp */
--- a/xo-websock/include/xo/websock/WsSafetyToken.hpp
+++ b/xo-websock/include/xo/websock/WsSafetyToken.hpp
@ -0,0 +1,29 @@
+/* file WsSafetyToken.hpp
+ *
+ * author: Roland Conybeare, Sep 2022
+ */
+
+#pragma once
+
+#include "SafetyToken.hpp"
+#include <mutex>
+
+namespace xo {
+    namespace web {
+        class WebserverImplWsThread;
+        class WebsocketSessionRecd;
+
+        /* only websocket thread can obtain this token */
+        class WsSafetyToken : public SafetyToken<class WsSafetyToken_tag> {
+        private:
+            friend class WebserverImplWsThread;
+
+        private:
+            /* only WebserverImpl should construct this */
+            WsSafetyToken() = default;
+        }; /*WsSafetyToken*/
+
+    } /*namespace web*/
+} /*namespace xo*/
+
+/* end WsSafetyToken.hpp */
--- a/xo-websock/src/websock/CMakeLists.txt
+++ b/xo-websock/src/websock/CMakeLists.txt
@ -0,0 +1,21 @@
+# xo-websock/CMakeLists.txt
+
+set(SELF_LIB websock)
+set(SELF_SRCS EndpointUtil.cpp DynamicEndpoint.cpp WebsockUtil.cpp WebsocketSink.cpp Webserver.cpp)
+
+xo_add_shared_library4(${SELF_LIB} ${PROJECT_NAME}Targets ${PROJECT_VERSION} 1 ${SELF_SRCS})
+
+# ----------------------------------------------------------------
+# external dependencies
+
+# note: changes to xo_dependency() calls here
+#       must coordinate with find_dependency() calls in
+#       xo-websock/cmake/websockConfig.cmake.in
+xo_dependency(${SELF_LIB} reactor)
+xo_dependency(${SELF_LIB} webutil)
+
+# see LibwebsocketsTargets-release.cmake for available targets
+# this dependency doesn't show up via cmake-export
+xo_external_target_dependency(${SELF_LIB} Libwebsockets websockets_shared)
+# see jsoncpp-namespaced-targets.cmake (maybe?) for available targets
+xo_external_target_dependency(${SELF_LIB} jsoncpp jsoncpp_lib)
--- a/xo-websock/src/websock/DynamicEndpoint.cpp
+++ b/xo-websock/src/websock/DynamicEndpoint.cpp
@ -0,0 +1,145 @@
+/* file DynamicEndpoint.cpp
+ *
+ * author: Roland Conybeare, Sep 2022
+ */
+
+#include "DynamicEndpoint.hpp"
+
+namespace xo {
+    using xo::web::Alist;
+    using xo::fn::CallbackId;
+
+    namespace web {
+        DynamicEndpoint::DynamicEndpoint(std::string uri_pattern,
+                                         HttpEndpointFn http_fn,
+                                         StreamSubscribeFn subscribe_fn,
+                                         StreamUnsubscribeFn unsubscribe_fn)
+            : uri_pattern_{std::move(uri_pattern)},
+              http_fn_{std::move(http_fn)},
+              subscribe_fn_{std::move(subscribe_fn)},
+              unsubscribe_fn_{std::move(unsubscribe_fn)}
+        {
+            std::string r_pat;
+
+            /* 1st pass -- construct pattern regex .uri_regex
+             * to identify urls that belong to this endpoint
+             *
+             * using regex like:
+             *   \$\{[[:alnum:]]+\}
+             */
+            {
+                std::regex var_rgx("\\$\\{[[:alnum:]]+\\}");
+
+                /* e.g. if .uri_pattern:
+                 *    /fixed/stem/${a}/more/fixed/stuff/${b}
+                 * then want r_pat:
+                 *    /fixed/stem/[[:alnum:]]+/more/fixed/stuff/[[:alnum:]]+
+                 * to find values pattern variables like ${a}, ${b}
+                 */
+                std::regex_replace(std::back_inserter(r_pat),
+                                   this->uri_pattern_.begin(),
+                                   this->uri_pattern_.end(),
+                                   var_rgx,
+                                   std::string("([[:alnum:]]+)"));
+
+                this->uri_regex_ = std::regex(r_pat);
+            }
+
+            /* 2nd pass -- identify pattern variables */
+            {
+                /* regex for:
+                 *   \$\{([[:alnum:]]+)\}
+                 * use to match input like
+                 *   ${apple}
+                 * and also extract the variable name
+                 *   apple
+                 */
+                std::regex var_rgx("\\$\\{([[:alnum:]]+)\\}");
+                std::smatch match;
+
+                std::string subject = this->uri_pattern_;
+
+                /* if subject like
+                 *   /fixed/stem/${a}/more/fixed/stuff/${b}
+                 * extract
+                 *   ["a", "b"]
+                 *
+                 * for
+                 *   /fixed/stem/${a}/more/fixed/stuff/${b}/${a}
+                 * also extract
+                 *   ["a", "b"]
+                 * i.e. avoid extracting the same variable name twice
+                 */
+                while (std::regex_search(subject, match, var_rgx)) {
+                    std::string v = match[1];
+
+                    bool present_flag = false;
+
+                    for (auto const & x : this->var_v_) {
+                        if (x == v) {
+                            present_flag = true;
+                            break;
+                        }
+                    }
+
+                    if (!present_flag)
+                        this->var_v_.push_back(match[1]);
+
+                    subject = match.suffix().str();
+                }
+            }
+        } /*ctor*/
+
+        void
+        DynamicEndpoint::http_response(std::string const & incoming_uri,
+                                       std::ostream * p_os) const
+        {
+            /* send this uri argument list  callback.
+             * contains variables extracted from .uri_pattern
+             * (variables surrounded by ${...})
+             */
+            Alist alist;
+
+            /* extract pattern variables in uri
+             * c.f. 2nd pass in DynamicEndpoint.ctor
+             */
+            std::smatch match;
+            std::string subject = incoming_uri;
+
+            /* if subject like
+             *   /fixed/stem/apple/more/fixed/stuff/beagle
+             * with .uri_pattern
+             *   /fixed/stem/${a}/more/fixed/stuff/${b}
+             * then we have .uri_regex
+             *   /fixed/stem/([[:alnum:]]+)/more/fixed/stuff/([[:alnum:]]+)
+             * use this to extract values for keys in .var_v,
+             * in the same order
+             */
+            if (std::regex_match(subject, match, this->uri_regex_)) {
+                for (size_t i = 0, n = this->var_v_.size(); i<n; ++i) {
+                    std::string i_name = this->var_v_[i];
+                    std::string i_value = match[1+i];
+
+                    alist.push_back(i_name, i_value);
+                }
+            }
+
+            this->http_fn_(incoming_uri, alist, p_os);
+        } /*http_response*/
+
+        CallbackId
+        DynamicEndpoint::subscribe(std::string const & /*incoming_uri*/,
+                                   rp<AbstractSink> const & ws_sink) const
+        {
+            return this->subscribe_fn_(ws_sink);
+        } /*subscribe*/
+
+        void
+        DynamicEndpoint::unsubscribe(CallbackId id) const
+        {
+            return this->unsubscribe_fn_(id);
+        } /*unsubscribe*/
+    } /*namespace web*/
+} /*namespace xo*/
+
+/* end DynamicEndpoint.cpp */
--- a/xo-websock/src/websock/EndpointUtil.cpp
+++ b/xo-websock/src/websock/EndpointUtil.cpp
@ -0,0 +1,38 @@
+/* file EndpointUtil.cpp
+ *
+ * author: Roland Conybeare, Sep 2022
+ */
+
+#include "EndpointUtil.hpp"
+
+namespace xo {
+    namespace web {
+        std::string
+        EndpointUtil::stem(std::string const & pattern)
+        {
+            std::size_t p = 0;
+            do {
+                p = pattern.find_first_of("$", p);
+
+                if ((p != std::string::npos) && (pattern[p+1] == '{')) {
+                    /* fixed stem is chars [0 .. p-1],  i.e. 1st p characters */
+                    break;
+                }
+
+                if (p != std::string::npos) {
+                    /* skip to next '$' */
+                    ++p;
+                }
+            } while (p != std::string::npos);
+
+            if (p == std::string::npos) {
+                /* pattern has no variable components */
+                return pattern;
+            } else {
+                return pattern.substr(0, p);
+            }
+        } /*stem*/
+    } /*namespace web*/
+} /*namespace xo*/
+
+/* end EndpointUtil.cpp */
--- a/xo-websock/src/websock/Webserver.cpp
+++ b/xo-websock/src/websock/Webserver.cpp
--- a/xo-websock/src/websock/WebsockUtil.cpp
+++ b/xo-websock/src/websock/WebsockUtil.cpp
@ -0,0 +1,155 @@
+/* @file WebsockUtil.cpp */
+
+#include "WebsockUtil.hpp"
+
+#define STRINGIFY(x) #x
+
+namespace xo {
+    namespace web {
+        char const *
+        WebsockUtil::ws_callback_reason_descr(lws_callback_reasons x) {
+
+#define CASE(x) case x: return STRINGIFY(x)
+
+            /* ubuntu build (available via github actions) has older version of libwebsockets.
+             * typically building (e.g. via nix) with libwebsockets 4.3.2
+             *
+             * see lws_config.h for version numbers vars
+             */
+
+            switch (x) {
+                CASE(LWS_CALLBACK_PROTOCOL_INIT);
+                CASE(LWS_CALLBACK_PROTOCOL_DESTROY);
+                CASE(LWS_CALLBACK_WSI_CREATE);
+                CASE(LWS_CALLBACK_WSI_DESTROY);
+                CASE(LWS_CALLBACK_WSI_TX_CREDIT_GET);
+                CASE(LWS_CALLBACK_OPENSSL_LOAD_EXTRA_CLIENT_VERIFY_CERTS);
+                CASE(LWS_CALLBACK_OPENSSL_LOAD_EXTRA_SERVER_VERIFY_CERTS);
+                CASE(LWS_CALLBACK_OPENSSL_PERFORM_CLIENT_CERT_VERIFICATION);
+#ifdef OBSOLETE // at least on osx w/ nixpkgs dd868b7bd4d1407d607da0d1d9c5eca89132e2f7
+                CASE(LWS_CALLBACK_OPENSSL_CONTEXT_REQUIRES_PRIVATE_KEY);
+#endif
+                CASE(LWS_CALLBACK_SSL_INFO);
+                CASE(LWS_CALLBACK_OPENSSL_PERFORM_SERVER_CERT_VERIFICATION);
+                CASE(LWS_CALLBACK_SERVER_NEW_CLIENT_INSTANTIATED);
+                CASE(LWS_CALLBACK_HTTP);
+                CASE(LWS_CALLBACK_HTTP_BODY);
+                CASE(LWS_CALLBACK_HTTP_BODY_COMPLETION);
+                CASE(LWS_CALLBACK_HTTP_FILE_COMPLETION);
+                CASE(LWS_CALLBACK_HTTP_WRITEABLE);
+                CASE(LWS_CALLBACK_CLOSED_HTTP);
+                CASE(LWS_CALLBACK_FILTER_HTTP_CONNECTION);
+                CASE(LWS_CALLBACK_ADD_HEADERS);
+                CASE(LWS_CALLBACK_VERIFY_BASIC_AUTHORIZATION);
+                CASE(LWS_CALLBACK_CHECK_ACCESS_RIGHTS);
+                CASE(LWS_CALLBACK_PROCESS_HTML);
+                CASE(LWS_CALLBACK_HTTP_BIND_PROTOCOL);
+                CASE(LWS_CALLBACK_HTTP_DROP_PROTOCOL);
+                CASE(LWS_CALLBACK_HTTP_CONFIRM_UPGRADE);
+                CASE(LWS_CALLBACK_ESTABLISHED_CLIENT_HTTP);
+                CASE(LWS_CALLBACK_CLOSED_CLIENT_HTTP);
+                CASE(LWS_CALLBACK_RECEIVE_CLIENT_HTTP_READ);
+                CASE(LWS_CALLBACK_RECEIVE_CLIENT_HTTP);
+                CASE(LWS_CALLBACK_COMPLETED_CLIENT_HTTP);
+                CASE(LWS_CALLBACK_CLIENT_HTTP_WRITEABLE);
+#if ((LWS_LIBRARY_VERSION_MAJOR > 4) || (LWS_LIBRARY_VERSION_MAJOR == 4) && (LWS_LIBRARY_VERSION_MINOR >= 3))
+                CASE(LWS_CALLBACK_CLIENT_HTTP_REDIRECT);
+#endif
+                CASE(LWS_CALLBACK_CLIENT_HTTP_BIND_PROTOCOL);
+                CASE(LWS_CALLBACK_CLIENT_HTTP_DROP_PROTOCOL);
+                CASE(LWS_CALLBACK_ESTABLISHED);
+                CASE(LWS_CALLBACK_CLOSED);
+                CASE(LWS_CALLBACK_SERVER_WRITEABLE);
+                CASE(LWS_CALLBACK_RECEIVE);
+                CASE(LWS_CALLBACK_RECEIVE_PONG);
+                CASE(LWS_CALLBACK_WS_PEER_INITIATED_CLOSE);
+                CASE(LWS_CALLBACK_FILTER_PROTOCOL_CONNECTION);
+                CASE(LWS_CALLBACK_CONFIRM_EXTENSION_OKAY);
+                CASE(LWS_CALLBACK_WS_SERVER_BIND_PROTOCOL);
+                CASE(LWS_CALLBACK_WS_SERVER_DROP_PROTOCOL);
+                CASE(LWS_CALLBACK_CLIENT_CONNECTION_ERROR);
+                CASE(LWS_CALLBACK_CLIENT_FILTER_PRE_ESTABLISH);
+                CASE(LWS_CALLBACK_CLIENT_ESTABLISHED);
+                CASE(LWS_CALLBACK_CLIENT_CLOSED);
+                CASE(LWS_CALLBACK_CLIENT_APPEND_HANDSHAKE_HEADER);
+                CASE(LWS_CALLBACK_CLIENT_RECEIVE);
+                CASE(LWS_CALLBACK_CLIENT_RECEIVE_PONG);
+                CASE(LWS_CALLBACK_CLIENT_WRITEABLE);
+                CASE(LWS_CALLBACK_CLIENT_CONFIRM_EXTENSION_SUPPORTED);
+                CASE(LWS_CALLBACK_WS_EXT_DEFAULTS);
+                CASE(LWS_CALLBACK_FILTER_NETWORK_CONNECTION);
+                CASE(LWS_CALLBACK_WS_CLIENT_BIND_PROTOCOL);
+                CASE(LWS_CALLBACK_WS_CLIENT_DROP_PROTOCOL);
+                CASE(LWS_CALLBACK_GET_THREAD_ID);
+                CASE(LWS_CALLBACK_ADD_POLL_FD);
+                CASE(LWS_CALLBACK_DEL_POLL_FD);
+                CASE(LWS_CALLBACK_CHANGE_MODE_POLL_FD);
+                CASE(LWS_CALLBACK_LOCK_POLL);
+                CASE(LWS_CALLBACK_UNLOCK_POLL);
+                CASE(LWS_CALLBACK_CGI);
+                CASE(LWS_CALLBACK_CGI_TERMINATED);
+                CASE(LWS_CALLBACK_CGI_STDIN_DATA);
+                CASE(LWS_CALLBACK_CGI_STDIN_COMPLETED);
+                CASE(LWS_CALLBACK_CGI_PROCESS_ATTACH);
+                CASE(LWS_CALLBACK_SESSION_INFO);
+                CASE(LWS_CALLBACK_GS_EVENT);
+                CASE(LWS_CALLBACK_HTTP_PMO);
+                CASE(LWS_CALLBACK_RAW_PROXY_CLI_RX);
+                CASE(LWS_CALLBACK_RAW_PROXY_SRV_RX);
+                CASE(LWS_CALLBACK_RAW_PROXY_CLI_CLOSE);
+                CASE(LWS_CALLBACK_RAW_PROXY_SRV_CLOSE);
+                CASE(LWS_CALLBACK_RAW_PROXY_CLI_WRITEABLE);
+                CASE(LWS_CALLBACK_RAW_PROXY_SRV_WRITEABLE);
+                CASE(LWS_CALLBACK_RAW_PROXY_CLI_ADOPT);
+                CASE(LWS_CALLBACK_RAW_PROXY_SRV_ADOPT);
+                CASE(LWS_CALLBACK_RAW_PROXY_CLI_BIND_PROTOCOL);
+                CASE(LWS_CALLBACK_RAW_PROXY_SRV_BIND_PROTOCOL);
+                CASE(LWS_CALLBACK_RAW_PROXY_CLI_DROP_PROTOCOL);
+                CASE(LWS_CALLBACK_RAW_PROXY_SRV_DROP_PROTOCOL);
+                CASE(LWS_CALLBACK_RAW_RX);
+                CASE(LWS_CALLBACK_RAW_CLOSE);
+                CASE(LWS_CALLBACK_RAW_WRITEABLE);
+                CASE(LWS_CALLBACK_RAW_ADOPT);
+                CASE(LWS_CALLBACK_RAW_CONNECTED);
+                CASE(LWS_CALLBACK_RAW_SKT_BIND_PROTOCOL);
+                CASE(LWS_CALLBACK_RAW_SKT_DROP_PROTOCOL);
+                CASE(LWS_CALLBACK_RAW_ADOPT_FILE);
+                CASE(LWS_CALLBACK_RAW_RX_FILE);
+                CASE(LWS_CALLBACK_RAW_WRITEABLE_FILE);
+                CASE(LWS_CALLBACK_RAW_CLOSE_FILE);
+                CASE(LWS_CALLBACK_RAW_FILE_BIND_PROTOCOL);
+                CASE(LWS_CALLBACK_RAW_FILE_DROP_PROTOCOL);
+                CASE(LWS_CALLBACK_TIMER);
+                CASE(LWS_CALLBACK_EVENT_WAIT_CANCELLED);
+                CASE(LWS_CALLBACK_CHILD_CLOSING);
+#if ((LWS_LIBRARY_VERSION_MAJOR > 4) || (LWS_LIBRARY_VERSION_MAJOR == 4) && (LWS_LIBRARY_VERSION_MINOR >= 3))
+                CASE(LWS_CALLBACK_CONNECTING);
+#endif
+                CASE(LWS_CALLBACK_VHOST_CERT_AGING);
+                CASE(LWS_CALLBACK_VHOST_CERT_UPDATE);
+                CASE(LWS_CALLBACK_MQTT_NEW_CLIENT_INSTANTIATED);
+                CASE(LWS_CALLBACK_MQTT_IDLE);
+                CASE(LWS_CALLBACK_MQTT_CLIENT_ESTABLISHED);
+                CASE(LWS_CALLBACK_MQTT_SUBSCRIBED);
+                CASE(LWS_CALLBACK_MQTT_CLIENT_WRITEABLE);
+                CASE(LWS_CALLBACK_MQTT_CLIENT_RX);
+                CASE(LWS_CALLBACK_MQTT_UNSUBSCRIBED);
+                CASE(LWS_CALLBACK_MQTT_DROP_PROTOCOL);
+                CASE(LWS_CALLBACK_MQTT_CLIENT_CLOSED);
+                CASE(LWS_CALLBACK_MQTT_ACK);
+                CASE(LWS_CALLBACK_MQTT_RESEND);
+#if ((LWS_LIBRARY_VERSION_MAJOR > 4) || (LWS_LIBRARY_VERSION_MAJOR == 4) && (LWS_LIBRARY_VERSION_MINOR >= 3))
+                CASE(LWS_CALLBACK_MQTT_UNSUBSCRIBE_TIMEOUT);
+                CASE(LWS_CALLBACK_MQTT_SHADOW_TIMEOUT);
+#endif
+                CASE(LWS_CALLBACK_USER);
+            }
+
+#undef CASE
+
+            return "???";
+        } /*ws_callback_reason_descr*/
+    } /*namespace web*/
+} /*namespace xo*/
+
+/* end WebsockUtil.cpp */
--- a/xo-websock/src/websock/WebsocketSink.cpp
+++ b/xo-websock/src/websock/WebsocketSink.cpp
@ -0,0 +1,147 @@
+/* file WebsocketSink.cpp
+ *
+ * author: Roland Conybeare, Sep 2022
+ */
+
+#include "WebsocketSink.hpp"
+#include "Webserver.hpp"
+#include "xo/printjson/PrintJson.hpp"
+#include "xo/reflect/Reflect.hpp"
+#include "xo/reflect/TaggedPtr.hpp"
+#include "xo/indentlog/scope.hpp"
+
+namespace xo {
+    using xo::reactor::AbstractSource;
+    using xo::json::PrintJson;
+    using xo::reflect::Reflect;
+    using xo::reflect::TaggedPtr;
+    using xo::reflect::TypeDescr;
+    using xo::ref::brw;
+    using xo::print::quot;
+    using xo::print::qcstr;
+    using xo::scope;
+    using xo::xtag;
+
+    namespace web {
+        /* a sink that publishes to a websocket.
+         * The websocket api creates a WebsocketSink instance
+         * on behalf of an incoming subscription request.
+         * application code will hold onto the sink somewhere
+         * and publish events to it,  to send them via websocket.
+         */
+        class WebsocketSinkImpl : public WebsocketSink {
+        public:
+            using PrintJson = xo::json::PrintJson;
+            using AbstractSource = reactor::AbstractSource;
+
+        public:
+            WebsocketSinkImpl(rp<Webserver> const & websrv,
+                              rp<PrintJson> const & pjson,
+                              uint32_t session_id,
+                              std::string stream_name)
+                : websrv_{std::move(websrv)},
+                  pjson_{std::move(pjson)},
+                  session_id_{session_id},
+                  stream_name_{std::move(stream_name)}
+                {}
+
+            virtual std::string const & name() const override { return name_; }
+            virtual void set_name(std::string const & x) override { this->name_ = x; }
+            /* 0 consumers for websocket sink,  since it's not a source */
+            virtual void visit_direct_consumers(std::function<void (brw<AbstractEventProcessor>)> const &) override {}
+            virtual void display(std::ostream & os) const override;
+
+            virtual bool allow_polymorphic_source() const override { return true; }
+            virtual TypeDescr sink_ev_type() const override;
+            virtual bool allow_volatile_source() const override { return true; }
+            virtual uint32_t n_in_ev() const override { return n_in_ev_; }
+            virtual void attach_source(rp<AbstractSource> const & src) override;
+            virtual void notify_ev_tp(TaggedPtr const & ev_tp) override;
+
+        private:
+            /* (ideally unique) user-controlled name for this sink
+             * in practice not likely to be accessible,
+             * so probably want to generate a unique-y default
+             */
+            std::string name_;
+            /* webserver implementation */
+            rp<Webserver> websrv_;
+            /* print arbitrary reflected stuff as json */
+            rp<PrintJson> pjson_;
+            /* websocket session id# - events arriving at this sink
+             * will be sent only to the session identified by .session_id
+             */
+            uint32_t session_id_;
+            /* name for stream.
+             * this will be the vale of the "stream" tag in
+             * initiating subscription message
+             *   {"cmd": "subscribe", "stream", "/this/stream/name"}
+             * e.g. in python:
+             *   web.register_stream_endpoint(kf.stream_endpoint_descr("/this/stream/name"))
+             */
+            std::string stream_name_;
+            /* count #of events received */
+            uint32_t n_in_ev_ = 0;
+        }; /*WebsocketSinkImpl*/
+
+        TypeDescr
+        WebsocketSinkImpl::sink_ev_type() const
+        {
+            return Reflect::require<void>();
+        } /*sink_ev_type*/
+
+        void
+        WebsocketSinkImpl::attach_source(rp<AbstractSource> const & src) {
+            src->attach_sink(this);
+        } /*attach_source*/
+
+        void
+        WebsocketSinkImpl::notify_ev_tp(TaggedPtr const & ev_tp)
+        {
+            scope log(XO_DEBUG(true /*debug_flag*/));
+
+            std::stringstream ss;
+
+            /* format message envelope */
+            ss << "{" << qcstr("stream") << ": " << quot(this->stream_name_)
+               << ", " << qcstr("event") << ": ";
+
+            /* format event as json */
+            this->pjson_->print_tp(ev_tp, &ss);
+
+            ss << "}";
+
+            log && log("sending", xtag("msg", ss.str()));
+
+            ++(this->n_in_ev_);
+
+            /* send event via associated websocket */
+            this->websrv_->send_text(this->session_id_, ss.str());
+
+        } /*notify_ev_tp*/
+
+        void
+        WebsocketSinkImpl::display(std::ostream & os) const
+        {
+            os << "<WebsocketSinkImpl"
+               << xtag("addr", (void*)this)
+               << xtag("name", name_)
+               << xtag("n_in_ev", n_in_ev_)
+               << xtag("stream", stream_name_)
+               << ">";
+        } /*display*/
+
+        // ----- WebsocketSink -----
+
+        rp<WebsocketSink>
+        WebsocketSink::make(rp<Webserver> const & websrv,
+                            rp<PrintJson> const & pjson,
+                            uint32_t session_id,
+                            std::string const & stream_name)
+        {
+            return new WebsocketSinkImpl(websrv, pjson, session_id, stream_name);
+        } /*make*/
+    } /*namespace web*/
+} /*namespace xo*/
+
+/* end WebsocketSink.cpp */
--- a/xo-websock/utest/CMakeLists.txt
+++ b/xo-websock/utest/CMakeLists.txt
@ -0,0 +1,47 @@
+# build unittest websock/utest
+
+set(SELF_EXE utest.websock)
+set(SELF_SRCS websock_utest_main.cpp)
+
+add_executable(${SELF_EXE} ${SELF_SRCS})
+xo_include_options2(${SELF_EXE})
+
+## note: can't add this yet,  because test not automated.
+##       requires manual interaction from browser
+##
+#add_test(NAME ${SELF_EXE} COMMAND ${SELF_EXE})
+#target_code_coverage(${SELF_EXE} AUTO ALL)
+
+# copy static {.html, .js, .svg} files to build directory
+file(COPY "${CMAKE_CURRENT_SOURCE_DIR}/mount-origin/"
+     DESTINATION "${CMAKE_CURRENT_BINARY_DIR}/mount-origin")
+
+# ----------------------------------------------------------------
+# internal dependency (on this codebase)
+
+xo_self_dependency(${SELF_EXE} websock)
+
+# ----------------------------------------------------------------
+# external dependencies
+
+target_link_libraries(${SELF_EXE} PUBLIC websock)
+# Need to port option, volfit before we can build this test here
+target_link_libraries(${SELF_EXE} PUBLIC option)
+target_link_libraries(${SELF_EXE} PUBLIC volfit)
+#target_link_libraries(utest.option PUBLIC logutil)
+
+
+# should be getting this via xo_include_options2()
+
+## ----------------------------------------------------------------
+## make standard directories for std:: includes explicit
+## so that
+## (1) they appear in compile_commands.json.
+## (2) clangd (run from emacs lsp-mode) can find them
+##
+#if(CMAKE_EXPORT_COMPILE_COMMANDS)
+#  set(CMAKE_CXX_STANDARD_INCLUDE_DIRECTORIES
+#      ${CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES})
+#endif()
+
+# end CMakeLists.txt
--- a/xo-websock/utest/README
+++ b/xo-websock/utest/README
@ -0,0 +1,13 @@
+To run this unit test:
+
+  $ cd path/to/kalman/build/src/websock/utest
+  $ ./utest.websock    # listens for http requests on port 7682
+
+point browser to
+
+  localhost:7682/ex_websock.html
+
+static files served from
+
+  path/to/kalman/build/src/websock/utest/mount-origin
+  
--- a/xo-websock/utest/mount-origin/bluecircle.svg
+++ b/xo-websock/utest/mount-origin/bluecircle.svg
@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<!-- <svg width="30" height="50"> ... </svg> does not satisfy chrome -->
+<svg width="30.0mm" height="50.0mm" version="1.1" xmlns="http://www.w3.org/2000/svg">
+    <circle cx="25" cy="25" r="22" fill="blue" stroke="gray" stroke-width="2"/>
+</svg>
+
--- a/xo-websock/utest/mount-origin/d3ex/d3ex.ch5.ex1.html
+++ b/xo-websock/utest/mount-origin/d3ex/d3ex.ch5.ex1.html
@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <script type="module">
+     import * as d3 from "https://cdn.skypack.dev/d3@7";
+
+     const body = d3.selectAll("body");
+    </script>
+  </head>
+  <body>
+    simple d3 example
+    <script type="module">
+    </script>
+  </body>
+</html>
--- a/xo-websock/utest/mount-origin/ex_websock.html
+++ b/xo-websock/utest/mount-origin/ex_websock.html
@ -0,0 +1,13 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>pywebsock example page</title>
+    <script type="module" src="ex_websock.js"></script>
+  </head>
+  <body>
+    <p>pywebsock example page</p>
+    <button id="refresh" type="button">refresh</button>
+    <div id="uls"></div>
+    <div id="kfs"></div>
+  </body>
+</html>
--- a/xo-websock/utest/mount-origin/ex_websock.js
+++ b/xo-websock/utest/mount-origin/ex_websock.js
@ -0,0 +1,842 @@
+/* webpage to display kalman filter output
+ * coordinates with ex_websock.py in this directory
+ */
+
+import * as d3 from "https://cdn.skypack.dev/d3@7";
+/* json5 accepts ieee floatingpoint special values;
+ * regular json excludes them (!?#)
+ */
+import JSON5 from "https://unpkg.com/json5@2/dist/index.min.mjs";
+
+/* NOTE: put "export" in front of a variable/function
+ *       that we want to make accessible outside this module
+ */
+
+/* for use for browser's javascript console */
+globalThis.d3 = d3;
+//globalThis.jparse = JSON5.parse;
+
+/* u: document.URL */
+function choose_ws_url(suffix_url)
+{
+    var pcol;
+    var u = document.URL;
+
+    /*
+     * We open the websocket encrypted if this page came on an
+     * https:// url itself, otherwise unencrypted
+     */
+
+    if (u.substring(0, 5) === "https") {
+        pcol = "wss://";
+        u = u.substr(8);
+    } else {
+        pcol = "ws://";
+        if (u.substring(0, 4) === "http")
+            u = u.substr(7);
+    }
+
+    u = u.split("/");
+
+    /* + "/xxx" bit is for IE10 workaround */
+
+    return pcol + u[0] + "/" + suffix_url;
+} /*choose_ws_url*/
+
+class Datatype {
+    #typename = null;
+    #nominal = null;
+    /* .from_json(x) convert a value received in json format
+     * to native representation.
+     */
+    #from_json = null;
+    /* .make_scale(range) builds d3 scale object */
+    #make_scale = null;
+
+    constructor(typename, nominal, from_json, make_scale) {
+	this.#typename = typename;
+	this.#nominal = nominal;
+	this.#from_json = from_json;
+	this.#make_scale = make_scale;
+    }
+
+    typename() { return this.#typename; }
+    nominal() { return this.#nominal; }
+    from_json(x) { return this.#from_json(x); }
+    make_scale(domain) { return this.#make_scale(domain); }
+}; /*Datatype*/
+
+class DatatypeFactory {
+    static dtype_map = DatatypeFactory.make_dtype_map();
+
+    static make_float_dtype() {
+	return new Datatype("float" /*typename*/,
+			    0.0 /*nominal*/,
+			    (x) => { return x; } /*from_json*/,
+			    (dom) => { return d3.scaleLinear().domain(dom); } /*make_scale*/
+			   ); }
+
+    static make_datetime_dtype() {
+	return new Datatype("datetime" /*typename*/,
+			    new Date() /*nominal*/,
+			    (x) => { return new Date(x); } /*from_json*/,
+			    (dom) => { return d3.scaleTime().domain(dom); } /*make_scale*/
+			   ); }
+    
+    static make_dtype_map() {
+	let retval = new Map();
+
+	retval.set("float", DatatypeFactory.make_float_dtype());
+	retval.set("datetime", DatatypeFactory.make_datetime_dtype());
+
+	return retval;
+    }
+
+    static lookup(typename) {
+	if (DatatypeFactory.dtype_map.has(typename)) {
+	    return DatatypeFactory.dtype_map.get(typename);
+	} else {
+	    throw new Error("DatatypeFactory: typename ["
+			    + typename
+			    + "] found where float|datetime expected");
+	}
+    }
+}; /*DatatypeFactory*/
+
+/* class to extract event values for charting.
+ * 'traits' because applies to separately-represented event objects
+ */
+class DataTraits {
+    /* .x_slotlookup(ev) => x-value */
+    #x_slotlookup = null;
+    /* .y_slotlookup(ev) => y-value */
+    #y_slotlookup = null;
+    #x_datatype = null; //DatatypeFactory.lookup("datetime");
+    #y_datatype = null; //DatatypeFactory.lookup("float");
+
+    /* x_nt, y_nt:  each should be a pair [slotlookup, typename]
+     * - slotname is a function :: event -> jsonvalue,
+     *   that extracts an attribute from incoming event in json format
+     * - typename is float|datetime
+     */
+    constructor(x_nt, y_nt) {
+	this.#x_slotlookup = x_nt[0];
+	this.#x_datatype = DatatypeFactory.lookup(x_nt[1]);
+	this.#y_slotlookup = y_nt[0];
+	this.#y_datatype = DatatypeFactory.lookup(y_nt[1]);
+    }
+
+    x_datatype() { return this.#x_datatype; }
+    y_datatype() { return this.#y_datatype; }
+
+    x_nominal() { return this.#x_datatype.nominal(); }
+    y_nominal() { return this.#y_datatype.nominal(); }
+
+    mapkey(data_ev) { return this.#x_slotlookup(data_ev); }
+    x_value(data_ev) { return this.#x_datatype.from_json(this.#x_slotlookup(data_ev)); }
+    y_value(data_ev) { return this.#y_datatype.from_json(this.#y_slotlookup(data_ev)); }
+
+    make_x_scale(domain) { return this.#x_datatype.make_scale(domain); }
+    make_y_scale(domain) { return this.#y_datatype.make_scale(domain); }
+}; /*DataTraits*/
+
+function range_outer(lh, rh) {
+    return [Math.min(lh[0], rh[0]),
+	    Math.max(lh[1], rh[1])];
+} /*range_outer*/
+
+/* a dataset driving a chart.
+ *
+ * PLAN: multiple lines in the same chart
+ * - makeitso dataset can contain multiple data series
+ *   - give each series within a dataset its own index#
+ *   - each series computes its own min/max x/y values
+ *   - take union across series to get chart x/y range
+ * - new class Dataset
+ */
+class Dataseries {
+    /* normalizing transformation for event objects.
+     * use to produce events {.x_value, .y_value} + key suitable for Map
+     */
+    #data_traits = null; //new DataTraits();
+    /* .dataset_map :: string -> {key value pair}
+     *    must use string as keys,  since Map uses object identity if key is Object
+     */
+    #dataset_map = new Map();
+    /* vector of key-value pairs,  in increasing x-axis order */
+    #dataset_v = [];
+    /* min,max value of dataset[i].x_value */
+    #dset_min_x = null;
+    #dset_max_x = null;
+    /* min,max value of dataset[i].y_value */
+    #dset_min_y = null;
+    #dset_max_y = null;
+
+    #max_key = 0;
+
+    constructor(data_traits) {
+	this.#data_traits = data_traits;
+	this.recalc_minmax();
+    }
+
+    data_traits() { return this.#data_traits; }
+    dataset_v() { return this.#dataset_v; }
+    x_range() { return [this.#dset_min_x, this.#dset_max_x]; }
+    y_range() { return [this.#dset_min_y, this.#dset_max_y]; }
+
+    /* data_ev must have attributes consistent with what .#data_traits expects */
+    update_dataset(data_ev) {
+	//console.log("Dataseries.update_dataset: data_ev=", data_ev);
+
+	let x = this.#data_traits.x_value(data_ev);
+	let y = this.#data_traits.y_value(data_ev);
+	/* using this key to recognize + suppress duplicate points
+	 * (e.g. if browser winds up sending multiple snapshot requests
+	 *       for the same dataset)
+	 */
+	let mapkey = this.#data_traits.mapkey(data_ev);
+
+	//console.log("Dataseries.update_dataset: x=", x, ", y=", y, ", mapkey=", mapkey);
+
+	/* in map must use time strings (not Dates) as keys */
+	if (this.#dataset_map.has(mapkey)) {
+	    /*skip -- assuming that source is immutable */;
+	} else {
+	    /* kv.key is ordinal number identifying a datum.
+	     * not related to mapkey,  except in so far as both work as datum ids
+	     */
+	    let kv = {key:     this.#max_key,
+		      x_value: x,
+		      y_value: y};
+
+	    /* (reminder: js map keys need to be strings) */
+	    this.#dataset_map.set(mapkey, kv);
+	    this.#dataset_v.push(kv);
+	    this.#max_key = this.#max_key+1;
+	}
+    } /*update_dataset*/
+
+    recalc_minmax() {
+	if (this.#dataset_v.length == 0) {
+	    /* min,max value of dataset[i].x_value */
+	    this.#dset_min_x = this.#data_traits.x_nominal();
+	    this.#dset_max_x = this.#data_traits.x_nominal();
+	    /* min,max value of dataset[i].y_value */
+	    this.#dset_min_y = this.#data_traits.y_nominal();
+	    this.#dset_max_y = this.#data_traits.y_nominal();
+	} else {
+	    /* min,max value of dataset[i].x_value */
+	    this.#dset_min_x = d3.min(this.#dataset_v, (d) => { return d.x_value; });
+	    this.#dset_max_x = d3.max(this.#dataset_v, (d) => { return d.x_value; });
+	    /* min,max value of dataset[i].y_value */
+	    this.#dset_min_y = d3.min(this.#dataset_v, (d) => { return d.y_value; });
+	    this.#dset_max_y = d3.max(this.#dataset_v, (d) => { return d.y_value; });
+	}
+    } /*recalc_minmax*/
+
+    /* note: caller should invoke .range() before using for drawing */
+    make_x_scale(xrange) {
+	return this.#data_traits.make_x_scale(xrange /*domain*/);
+    } /*make_x_scale*/
+
+    /* note: caller should invoke .range() before using for drawing */
+    make_y_scale(yrange) {
+	return this.#data_traits.make_y_scale(yrange /*domain*/);
+    } /*make_y_scale*/
+}; /*Dataseries*/
+
+/* bundle multiple dataseries for charting
+ * for now: can have multiple series,  but they need to be driven
+ * from the same native row storage
+ */
+class Dataset {
+    #dataseries_v = [];
+    /* min/max x-values across all members of .dataseries_v */
+    #outer_x_range = null;
+    /* min/max y-values across all members of .dataseries_v */
+    #outer_y_range = null;
+
+    constructor(data_traits_v) {
+	for (let i=0, n=data_traits_v.length; i<n; ++i) {
+	    this.#dataseries_v[i] = new Dataseries(data_traits_v[i]);
+	}
+
+	this.#recalc_minmax_aux();
+    }
+
+    /* #of dataseries bundled into this dataset */
+    n_dataseries() {
+	return this.#dataseries_v.length;
+    }
+
+    /* fetch i'th dataseries.
+     *
+     * Require:
+     * - 0 <= i_dataseries < .n_dataseries()
+     */
+    lookup_dataseries(i_dataseries) {
+	if (0 <= i_dataseries && i_dataseries < this.n_dataseries()) {
+	    return this.#dataseries_v[i_dataseries];
+	} else {
+	    throw new Error('lookup_dataseries: expected i in [0..n) i=' +  i + ' n=' + this.n_dataseries());
+	}
+    } /*lookup_dataseries*/
+
+    /* range of x-values,  taken across all contained series */
+    x_range() {
+	return this.#outer_x_range;
+    }
+
+    /* range of y-values,  taken across all contained series */
+    y_range() {
+	return this.#outer_y_range;
+    }
+
+    /* update dataset for a single new row */
+    update_dataset(data_ev) {
+	for (let i=0, n=this.n_dataseries(); i<n; ++i) {
+	    this.#dataseries_v[i].update_dataset(data_ev);
+	}
+    } /*update_dataset*/
+
+    /* recalc x,y ranges for each dataseries;
+     * and recalculate outer x,y range stored in this dataset
+     */
+    recalc_minmax() {
+	let n=this.n_dataseries();
+
+	if (n > 0) {
+	    for (let i=0; i<n; ++i) {
+		this.#dataseries_v[i].recalc_minmax();
+	    }
+
+	    this.#recalc_minmax_aux();
+	}
+    } /*recalc_minmax*/
+
+    #recalc_minmax_aux() {
+	let n = this.n_dataseries();
+
+	if (n > 0) {
+	    /* update dataset minmax (i.e. union of mim-max intervals across series) */
+	    let outer_x = this.#dataseries_v[0].x_range();
+	    let outer_y = this.#dataseries_v[0].y_range();
+
+	    for (let i=1; i<n; ++i) {
+		let dataseries = this.#dataseries_v[i];
+
+		outer_x = range_outer(outer_x, dataseries.x_range());
+		outer_y = range_outer(outer_y, dataseries.y_range());
+	    }
+
+	    this.#outer_x_range = outer_x;
+	    this.#outer_y_range = outer_y;
+	}
+    } /*recalc_minmax_aux*/
+
+    /* create d3 scale for x-values in this dataset
+     * (to be used for x-values in all series)
+     */
+    make_x_scale() {
+	/* plan: verify that all series are compatible?
+	 *       e.g. all timeseries or all linear
+	 */
+
+	/* using series #0 (really,  its traits) as prototype */
+	return this.#dataseries_v[0].make_x_scale(this.#outer_x_range);
+    } /*make_x_scale*/
+
+    /* create d3 scale for y-values in this dataset
+     * (to be used for y-values in all series)
+     */
+    make_y_scale() {
+	/* plan: verify that all series are compatible?
+	 *       e.g. all timeseries or all linear
+	 */
+
+	/* using series #0 (really, its traits) as prototype */
+	return this.#dataseries_v[0].make_y_scale(this.#outer_y_range);
+    } /*make_y_scale*/
+
+}; /*Dataset*/
+
+/* drawing code for a line chart.
+ * uses svg for the "graphed line"
+ *
+ * originally extracted from TimeseriesCtl.
+ *
+ *
+ *     <------- .chart_w ------->
+ *     +------------------------+ ^
+ *     |                        | |
+ *     |   +----------------+   | |
+ *     |   |        /|      |   | |
+ *     |   |       / | .pad <---> |
+ *     |   |      /  \      |   | |
+ *     |   | /\  /    \     |   | .chart_h
+ *     |   |/  --      \  --|   | |
+ *     |   |            \/  |   | |
+ *     |   +----------------+   | |
+ *     |                        | |
+ *     +------------------------+ v
+ *
+ * DOM:
+ *    <? id=#uls> (will attach svg element here)
+ *     +- <svg>
+ *         +- <g id=#x_axis class=xaxis> (d3 will draw x-axis inside, .chart_x_axis() draws)
+ *         +- <g id=#y_axis class=yaxis> (d3 will draw y-axis inside, .chart_y_axis() draws)
+ *         +- <g id=#pts-0 class=pts>
+ *             +- <path id=#line class=line> (.chart_line_gen draws)
+ *
+ * may have chart with multiple series;
+ * we still expect to share
+ *   {.chart_x_scale, .chart_y_scale, .chart_x_axis, .chart_y_axis, .chart_svg}
+ * across all series.
+ * we also share .chart_line_gen,  since each series supplies normalized (x_value, y_value)
+ * pairs,  and we're sharing the same (x,y) d3-scales
+ */
+class LineChart {
+    #chart_w = 100;
+    #chart_h = 100;
+    #chart_pad = 10;
+
+    /* .chart_xx variables established in .require_gui() */
+    /* d3 scale for x values */
+    #chart_x_scale = null;
+    /* d3 scale for y values */
+    #chart_y_scale = null;
+    /* d3 svg-line-generator */
+    #chart_line_gen = null;
+    /* d3 axis for x values (bottom of chart area) */
+    #chart_x_axis = null;
+    /* d3 axis for y values (left of chart area) */
+    #chart_y_axis = null;
+    /* svg chart object (the <svg> tag above in DOM sketch)*/
+    #chart_svg = null;
+
+    constructor(w, h, pad) {
+	this.#chart_w = w;
+	this.#chart_h = h;
+	this.#chart_pad = pad;
+    }
+
+    x_range() { return [this.#chart_pad,
+			this.#chart_w - this.#chart_pad]; }
+    /* note: inverting bc svg y-values increase towards bottom of screen;
+     *       we want y-values to increase towards top of screen
+     */
+    y_range() { return [this.#chart_h - this.#chart_pad,
+			this.#chart_pad]; }
+	
+    require_gui(parent_d3sel, dataset) {
+	this.#require_x_scale(dataset);
+	this.#require_y_scale(dataset);
+	this.#require_linegen(); /*will use .chart_x_scale, .chart_y_scale */
+	this.#require_x_axis(); /*will use .chart_x_scale*/
+	this.#require_y_axis(); /*will use .chart_y_scale*/
+	this.#require_svg(parent_d3sel, dataset);
+    }
+
+    /* dom element id to use for the i'th dataseries in this chart */
+    series_html_id(i_dataseries) {
+	return "pts-" + i_dataseries;
+    }
+
+    /* update chart for new dataset contents
+     *
+     * Require:
+     * - .require_gui(_, dataset) has been called 
+     * - #of dataseries has not changed since last call to .require_svg()
+     */
+    update_chart(dataset) {
+	/* update d3 scales
+	 * (shared across all series bundled into this dataset
+	 */
+	this.#rescale_chart(dataset);
+
+	for (let i=0, n=dataset.n_dataseries(); i<n; ++i) {
+	    let dataseries = dataset.lookup_dataseries(i);
+
+	    let series_svgid = this.series_html_id(i);
+
+	    // update dataseries (pts)
+	    let line = (this
+			.#chart_svg
+			.select("#" + series_svgid)
+			.select("#line")
+			.datum(dataseries.dataset_v())
+			.attr("d", this.#chart_line_gen));
+	}
+    } /*update_chart*/
+
+    // ----- implementation methods -----
+
+    /* svg translate command (a string),
+     * to move x-axis from origin to location relative to chart svg object
+     * (i.e. to chart top left corner)
+     */
+    #x_axis_translate_str() {
+	/* e.g.
+	 *   "translate(0,450)"
+	 */
+	return "translate(0," + (this.#chart_h - this.#chart_pad) + ")";
+    }
+
+    /* svg translate command (a string)
+     * to move y-axis from origin to location relative to chart svg object
+     * (i.e. to chart top left corner)
+     */
+    #y_axis_translate_str() {
+	/* e.g.
+	 *   "translate(50,0)"
+	 */
+	return "translate(" + this.#chart_pad + ",0)";
+    }
+
+    #require_x_scale(dataset) {
+	if (!this.#chart_x_scale) {
+	    this.#chart_x_scale = (dataset.make_x_scale()
+				   .range(this.x_range())
+				   .nice());
+	}
+
+	return this.#chart_x_scale;
+    } /*require_x_scale*/
+
+    #require_y_scale(dataset) {
+	if (!this.#chart_y_scale) {
+	    this.#chart_y_scale = (dataset.make_y_scale()
+				   .range(this.y_range())
+				   .nice());
+	}
+
+	return this.#chart_y_scale;
+    } /*require_y_scale*/
+
+    #require_linegen() {
+	if (!this.#chart_line_gen) {
+	    this.#chart_line_gen = (d3.line()
+				    .x((d) => { return this.#chart_x_scale(d.x_value); })
+				    .y((d) => { return this.#chart_y_scale(d.y_value); }));
+	}
+    } /*require_linegen*/
+
+    #require_x_axis() {
+	if (!this.#chart_x_axis) {
+	    this.#chart_x_axis = (d3
+				  .axisBottom()
+				  .scale(this.#chart_x_scale)
+				  .ticks(10));
+	}
+    }
+
+    #require_y_axis() {
+	if (!this.#chart_y_axis) {
+	    this.#chart_y_axis = (d3
+				  .axisLeft()
+				  .scale(this.#chart_y_scale)
+				  .ticks(10));
+	}
+    }
+
+    #require_svg(parent_d3sel, dataset) {
+	if (!this.#chart_svg) {
+	    this.#chart_svg = (parent_d3sel // .select("#uls")
+			       .append("svg")
+			       .attr("width", this.#chart_w)
+			       .attr("height", this.#chart_h));
+
+	    /* svg group comprising x-axis */
+	    this.#chart_svg.append("g")
+		.attr("class", "xaxis")
+		.attr("id", "x_axis")
+		.attr("transform", this.#x_axis_translate_str())
+		.call(this.#chart_x_axis);
+
+	    /* svg group comprising y-axis */
+	    this.#chart_svg.append("g")
+		.attr("class", "yaxis")
+		.attr("id", "y_axis")
+		.attr("transform", this.#y_axis_translate_str())
+		.call(this.#chart_y_axis);
+
+	    for (let i=0, n=dataset.n_dataseries(); i<n; ++i) {
+		let dataseries = dataset.lookup_dataseries(i);
+
+		let series_svgid = this.series_html_id(i);
+
+		/* svg group comprising chart dataseries
+		 *   chart_line_gen gets invoked for each member of .datum()
+		 */
+		this.#chart_svg.append("g")
+		    .attr("class", "pts")
+		    .attr("id", series_svgid)
+		    .append("path")
+		    .attr("class", "line")
+		    .attr("id", "line")
+		    .attr("fill", "none")
+		    .attr("stroke", "black")
+		    .datum(dataseries.dataset_v())
+		    .attr("d", this.#chart_line_gen);
+	    }
+	}
+    }
+
+    #rescale_chart(dataset) {
+	this.#chart_x_scale.domain(dataset.x_range());
+	this.#chart_y_scale.domain(dataset.y_range());
+
+	// update x-axis
+	this.#chart_svg.selectAll("#x_axis")
+            .attr("transform",
+		  this.#x_axis_translate_str())
+	    .call(this.#chart_x_axis);
+
+	// update y-axis
+	this.#chart_svg.selectAll("#y_axis")
+	    .attr("transform",
+		  this.#y_axis_translate_str())
+	    .call(this.#chart_y_axis);
+    }
+
+}; /*LineChart*/
+
+class Controller {
+};
+
+/*
+ * DOM:
+ *    <? id=#uls> (will attach svg element here)
+ *     +- <svg>
+ *         +- <g id=#x_axis class=xaxis> (d3 will draw x-axis inside, .chart_x_axis() draws)
+ *         +- <g id=#y_axis class=yaxis> (d3 will draw y-axis inside, .chart_y_axis() draws)
+ *         +- <g id=#pts-0 class=pts>
+ *             +- <path id=#line class=line> (.chart_line_gen draws)
+ */
+class TimeseriesCtl extends Controller {
+    #dataset_uri = '';
+    #dataset = null;
+
+    #chart = new LineChart(500 /*w*/,
+			   250 /*h*/,
+			   50 /*pad*/);
+
+    constructor(dataset_uri, data_traits_v) {
+	super();
+	this.#dataset_uri = dataset_uri;
+	this.#dataset = new Dataset(data_traits_v);
+    }
+
+    static rescale_dataset(dataset) {
+	dataset.recalc_minmax();
+    } /*rescale_dataset*/
+
+    /* request dataseries snapshot from webserver;
+     * update+draw graph when snapshot arrives
+     *
+     * NOTE:
+     * 1. typical web docs (e.g. MDN) will advise using response.json():
+     *      fetch(uri)
+     *        .then((response) => response.json())
+     *        .then((data) => dostuffwith(data))
+     *     
+     *    however,  this has a flaw: standard json is missing special floating-point values (!!);
+     *    in particular it has no representation for nan/+inf/-inf
+     * 2. we want to use the extended json standard 'json5';
+     *    however need care since JSON5.parse() fails spuriously (at least JSON5/chrome asof 24sep2022)
+     *    if given a promise
+     */
+    request() {
+	fetch(this.#dataset_uri)
+	    .then((response) => response.text())
+	    .then((text) => this.on_snapshot_text(text));
+
+//	    .then((text) => JSON5.parse()
+//	    .then((data) => this.on_snapshot(data));
+    } /*request*/
+
+    /* update from snapshot json text */
+    on_snapshot_text(text) {
+	const data = JSON5.parse(text);
+
+	this.on_snapshot(data);
+    } /*on_snapshot_text*/
+
+    /* update from snapshot
+     *
+     *  .on_snapshot() => .#dataset => .on_dataset()
+     */
+    on_snapshot(data) {
+	//console.log("on_snapshot: data=", data);
+
+	data.forEach((x, i) => {
+	    // REFACTORME
+
+	    if (x._name_ == "UpxEvent") {
+		this.on_update(x);
+	    } else if (x._name_ == "KalmanFilterStateExt") {
+		this.on_update(x);
+	    } else {
+		console.log("unexpected json record x=", x);
+	    }
+	});
+
+	this.on_dataset(this.#dataset);
+    } /*on_snapshot*/
+
+    /* update from websocket
+     *
+     *  .on_update() => .#dataset => .on_dataset()
+     */
+    on_update(data_ev) {
+	this.#dataset.update_dataset(data_ev);
+
+	this.on_dataset(this.#dataset);
+    } /*on_update*/
+
+    /* call after modifying .#dataset
+     *
+     *  .on_dataset() =|=> .rescale_dataset() =|========> .chart_x_axis ===\
+     *                 |                       |========> .chart_x_axis =\ |
+     *                 |                                                 | |
+     *                 |=> .chart_svg.#x_axis <==========================/ |
+     *                 |=> .chart_svg.#y_axis <============================/
+     */
+    on_dataset(dataset) {
+	//console.log("on_dataset: dataset=", dataset);
+
+	// update x-scale, y-scale
+	TimeseriesCtl.rescale_dataset(dataset);
+    
+	this.#chart.update_chart(dataset);
+    } /*on_dataset*/
+
+    /* e.g.
+     *   ctl.require_gui(d3.select("#uls"))
+     * to build chart gui under DOM element with id="uls"
+     */
+    require_gui(parent_d3sel) {
+	this.#chart.require_gui(parent_d3sel, this.#dataset);
+    } /*require_gui*/
+
+}; /*TimeseriesCtl*/
+
+/* controller for timeseries graph,  from uri [/dyn/uls/snap] + [/ws/uls] */
+var uls_ctl = false;
+var uls_ctl_enabled = true;
+
+if (uls_ctl_enabled) {
+    uls_ctl = new TimeseriesCtl('/dyn/uls/snap',
+				[new DataTraits([(ev) => ev.tm, "datetime"],
+						[(ev) => ev.upx, "float"])]);
+
+    uls_ctl.require_gui(d3.select("#uls"));
+    uls_ctl.request();
+}
+
+/* controller for timeseries graph,  from uri [/dyn/kfs/snap] + [/ws/kfs] */
+var kfs_ctl = false;
+var kfs_ctl_enabled = true;
+
+if (kfs_ctl_enabled) {
+    kfs_ctl = new TimeseriesCtl('/dyn/kfs/snap',
+				[new DataTraits([(ev) => ev.tk,
+						 "datetime"],
+						[(ev) => { return ev.x[0]; },
+						 "float"]),
+				 /* 2.sigma below estimate */
+				 new DataTraits([(ev) => ev.tk,
+						 "datetime"],
+						[(ev) => { return Math.max(0.0, ev.x[0] - 2.0 * Math.sqrt(ev.P[0][0])); },
+						 "float"]),
+				 /* 2.sigma above estimate */
+				 new DataTraits([(ev) => ev.tk,
+						 "datetime"],
+						[(ev) => { return Math.min(1.0, ev.x[0] + 2.0 * Math.sqrt(ev.P[0][0])); },
+						 "float"])
+				]);
+    
+    kfs_ctl.require_gui(d3.select("#kfs"));
+    kfs_ctl.request();
+}
+
+let key_fn = ((d) => { return d.key; });
+
+/* controller for volsurface graph (strike -> volatility),
+ * from uri [/dyn/kf/snap]
+ */
+
+d3.select("#refresh")
+    .on("click",
+	function() {
+	    console.log("button[#refresh] clicked");
+
+	    uls_ctl.request();
+	});
+
+var srv_ws = null;
+
+function content_loaded_fn()
+{
+    console.log("Hi Roly, DOM loaded");
+
+    /* use this url to create websocket to the server that delivered current webpage */
+    let ws_url = choose_ws_url("" /*url_suffix*/);
+    console.log("ws_url: [", ws_url, "]");
+
+    srv_ws = new WebSocket(ws_url, "lws-minimal");
+
+    try {
+	// srv_ws.onopen = () => { ... };
+	// srv_ws.onclose = () => { ... };
+	srv_ws.onmessage = (msg) => {
+	    /* msg has dozens of attributes,  too many to list here
+	     * actual application message appears in the .data attribute
+	     * (as nested js string)
+	     */
+	    //console.log("incoming ws msg: [", msg, "]");
+	    
+	    let msgdata = JSON5.parse(msg.data);
+
+	    //console.log("msgdata: [", msgdata, "]");
+
+	    let stream_name = msgdata.stream;
+	    let event = msgdata.event;
+
+	    if (stream_name == "/ws/uls") {
+		if (uls_ctl) {
+		    uls_ctl.on_update(event);
+		}
+	    } else if (stream_name == "/ws/kfs") {
+		if (kfs_ctl) {
+		    kfs_ctl.on_update(event);
+		}
+	    } else {
+		console.log("unknown stream name [", stream_name, "]");
+	    }
+	};
+    } catch(excetpion) {
+	asert("<p>Error: " + exception);
+    }
+
+    console.log("srv_ws state [", srv_ws.readyState, "]");
+    
+    srv_ws.addEventListener('open',
+			    (event) => {
+				console.log("srv_ws state [", srv_ws.readyState, "]");
+				if (uls_ctl) {
+				    srv_ws.send("{\"cmd\": \"subscribe\", \"stream\": \"/ws/uls\"} ");
+				}
+				if (kfs_ctl) {
+				    srv_ws.send("{\"cmd\": \"subscribe\", \"stream\": \"/ws/kfs\"} ");
+				}
+				//socket.send('Hello Server!');
+			    });
+				  
+} /*content_loaded_fn*/
+
+document.addEventListener("DOMContentLoaded",
+			  content_loaded_fn,
+			  false);
+
+/* end ex_websock.js */
--- a/xo-websock/utest/mount-origin/example.js
+++ b/xo-websock/utest/mount-origin/example.js
@ -0,0 +1,64 @@
+function get_appropriate_ws_url(extra_url)
+{
+        var pcol;
+        var u = document.URL;
+
+        /*
+         * We open the websocket encrypted if this page came on an
+         * https:// url itself, otherwise unencrypted
+         */
+
+        if (u.substring(0, 5) === "https") {
+                pcol = "wss://";
+                u = u.substr(8);
+        } else {
+                pcol = "ws://";
+                if (u.substring(0, 4) === "http")
+                        u = u.substr(7);
+        }
+
+        u = u.split("/");
+
+        /* + "/xxx" bit is for IE10 workaround */
+
+        return pcol + u[0] + "/" + extra_url;
+}
+
+function new_ws(urlpath, protocol)
+{
+        return new WebSocket(urlpath, protocol);
+}
+
+document.addEventListener("DOMContentLoaded", function() {
+        
+        var ws = new_ws(get_appropriate_ws_url(""), "lws-minimal");
+        try {
+                ws.onopen = function() {
+                        document.getElementById("m").disabled = 0;
+                        document.getElementById("b").disabled = 0;
+                };
+        
+                ws.onmessage =function got_packet(msg) {
+                        document.getElementById("r").value =
+                                document.getElementById("r").value + msg.data + "\n";
+                        document.getElementById("r").scrollTop =
+                                document.getElementById("r").scrollHeight;
+                };
+        
+                ws.onclose = function(){
+                        document.getElementById("m").disabled = 1;
+                        document.getElementById("b").disabled = 1;
+                };
+        } catch(exception) {
+                alert("<p>Error " + exception);  
+        }
+        
+        function sendmsg()
+        {
+                ws.send(document.getElementById("m").value);
+                document.getElementById("m").value = "";
+        }
+        
+        document.getElementById("b").addEventListener("click", sendmsg);
+        
+}, false);
--- a/xo-websock/utest/mount-origin/index.html
+++ b/xo-websock/utest/mount-origin/index.html
@ -0,0 +1,19 @@
+<html>
+ <head>
+  <meta charset=utf-8 http-equiv="Content-Language" content="en"/>
+  <script src="/example.js"></script>
+ </head>
+        <body>
+                <img src="libwebsockets.org-logo.svg">
+                <img src="strict-csp.svg"><br>
+        
+                LWS chat <b>minimal ws server example</b>.<br>
+                Chat is sent to all browsers open on this page.
+                <br>
+                <br>
+                <textarea id=r readonly cols=40 rows=10></textarea><br>
+                <input type="text" id=m cols=40 rows=1>
+                <button id=b>Send</button>
+        </body>
+</html>
+
--- a/xo-websock/utest/mount-origin/libwebsockets.org-logo.svg
+++ b/xo-websock/utest/mount-origin/libwebsockets.org-logo.svg
@ -0,0 +1,66 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg width="117.26mm" height="19.676mm" version="1.1" viewBox="0 0 117.26 19.677" xmlns="http://www.w3.org/2000/svg" xmlns:cc="http://creativecommons.org/ns#" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+<metadata>
+<rdf:RDF>
+<cc:Work rdf:about="">
+<dc:format>image/svg+xml</dc:format>
+<dc:type rdf:resource="http://purl.org/dc/dcmitype/StillImage"/>
+<dc:title/>
+</cc:Work>
+</rdf:RDF>
+</metadata>
+<path d="m0-2.6715e-4h117.26v19.677h-117.26z" fill="none"/>
+<g transform="matrix(.63895 0 0 .63895 2.5477 3.6562)">
+<g transform="matrix(.9517 0 0 .9517 3.2398 -93.904)">
+<path d="m9.5909 107.4h2.5567v2.649h-2.5567z"/>
+<path d="m12.12 107.36a1.2625 1.2625 0 0 1-1.2625 1.262 1.2625 1.2625 0 0 1-1.2625-1.262 1.2625 1.2625 0 0 1 1.2625-1.262 1.2625 1.2625 0 0 1 1.2625 1.262" stroke-linecap="round" stroke-width="1.0365"/>
+<path d="m12.127 110.05a1.2625 1.2625 0 0 1-1.2625 1.262 1.2625 1.2625 0 0 1-1.2625-1.262 1.2625 1.2625 0 0 1 1.2625-1.262 1.2625 1.2625 0 0 1 1.2625 1.262" stroke-linecap="round" stroke-width="1.0365"/>
+</g>
+<path d="m12.174 13.987a1.2015 1.2015 0 0 1-1.2024 1.2024 1.2015 1.2015 0 0 1-1.2006-1.2024 1.2015 1.2015 0 0 1 1.2006-1.2005 1.2015 1.2015 0 0 1 1.2024 1.2005" stroke-linecap="round" stroke-width=".98647"/>
+<path d="m8.2754 5.0474h2.468v5.6755h-2.468z"/>
+<path d="m16.25 13.965a1.2015 1.2015 0 0 1-1.2027 1.2005 1.2015 1.2015 0 0 1-1.2004-1.2005 1.2015 1.2015 0 0 1 1.2004-1.2025 1.2015 1.2015 0 0 1 1.2027 1.2025" stroke-linecap="round" stroke-width=".98647"/>
+<path d="m19.545 13.928a1.2015 1.2015 0 0 1-1.2025 1.2026 1.2015 1.2015 0 0 1-1.2003-1.2026 1.2015 1.2015 0 0 1 1.2003-1.2005 1.2015 1.2015 0 0 1 1.2025 1.2005" stroke-linecap="round" stroke-width=".98647"/>
+<path d="m23.75 13.902a1.2015 1.2015 0 0 1-1.2005 1.2024 1.2015 1.2015 0 0 1-1.2025-1.2024 1.2015 1.2015 0 0 1 1.2025-1.2005 1.2015 1.2015 0 0 1 1.2005 1.2005" stroke-linecap="round" stroke-width=".98647"/>
+<path d="m26.249 5.0292a1.2015 1.2015 0 0 1-1.2027 1.2004 1.2015 1.2015 0 0 1-1.2004-1.2004 1.2015 1.2015 0 0 1 1.2004-1.2026 1.2015 1.2015 0 0 1 1.2027 1.2026" stroke-linecap="round" stroke-width=".98647"/>
+<g transform="matrix(.9517 0 0 .9517 6.3252 -93.961)">
+<path d="m9.5909 107.4h2.5567v2.649h-2.5567z"/>
+<path d="m12.12 107.36a1.2625 1.2625 0 0 1-1.2625 1.262 1.2625 1.2625 0 0 1-1.2625-1.262 1.2625 1.2625 0 0 1 1.2625-1.262 1.2625 1.2625 0 0 1 1.2625 1.262" stroke-linecap="round" stroke-width="1.0365"/>
+<path d="m12.127 110.05a1.2625 1.2625 0 0 1-1.2625 1.262 1.2625 1.2625 0 0 1-1.2625-1.262 1.2625 1.2625 0 0 1 1.2625-1.262 1.2625 1.2625 0 0 1 1.2625 1.262" stroke-linecap="round" stroke-width="1.0365"/>
+</g>
+<g transform="matrix(.9517 0 0 .9517 9.3806 -93.988)">
+<path d="m9.5909 107.4h2.5567v2.649h-2.5567z"/>
+<path d="m12.12 107.36a1.2625 1.2625 0 0 1-1.2625 1.262 1.2625 1.2625 0 0 1-1.2625-1.262 1.2625 1.2625 0 0 1 1.2625-1.262 1.2625 1.2625 0 0 1 1.2625 1.262" stroke-linecap="round" stroke-width="1.0365"/>
+<path d="m12.127 110.05a1.2625 1.2625 0 0 1-1.2625 1.262 1.2625 1.2625 0 0 1-1.2625-1.262 1.2625 1.2625 0 0 1 1.2625-1.262 1.2625 1.2625 0 0 1 1.2625 1.262" stroke-linecap="round" stroke-width="1.0365"/>
+</g>
+<g transform="matrix(.9517 0 0 .9517 13.506 -94.006)">
+<path d="m9.5909 107.4h2.5567v2.649h-2.5567z"/>
+<path d="m12.12 107.36a1.2625 1.2625 0 0 1-1.2625 1.262 1.2625 1.2625 0 0 1-1.2625-1.262 1.2625 1.2625 0 0 1 1.2625-1.262 1.2625 1.2625 0 0 1 1.2625 1.262" stroke-linecap="round" stroke-width="1.0365"/>
+<path d="m12.127 110.05a1.2625 1.2625 0 0 1-1.2625 1.262 1.2625 1.2625 0 0 1-1.2625-1.262 1.2625 1.2625 0 0 1 1.2625-1.262 1.2625 1.2625 0 0 1 1.2625 1.262" stroke-linecap="round" stroke-width="1.0365"/>
+</g>
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--- a/xo-websock/utest/websock_utest_main.cpp
+++ b/xo-websock/utest/websock_utest_main.cpp
@ -0,0 +1,282 @@
+/* @file websock_utest_main.cpp */
+
+#include "websock/Webserver.hpp"
+#include "volfit/init_volfit.hpp"
+#include "volfit/Volfit.hpp"
+#include "volfit/VolfitInputCapture.hpp"
+#include "filter/init_filter.hpp"
+#include "filter/KalmanFilterSvc.hpp"
+#include "option/StrikeSetOmd.hpp"
+#include "option/StrikeSetMarketModel.hpp"
+#include "option/UlMarketModel.hpp"
+#include "option/PricingContext.hpp"
+#include "option/OptionStrikeSet.hpp"
+#include "process/init_process.hpp"
+#include "process/RealizationSource.hpp"
+#include "process/RealizationTracer.hpp"
+#include "process/UpxEvent.hpp"
+#include "process/ExpProcess.hpp"
+#include "process/BrownianMotion.hpp"
+#include "simulator/init_simulator.hpp"
+#include "simulator/Simulator.hpp"
+#include "reactor/EventStore.hpp"
+#include "randomgen/random_seed.hpp"
+#include "randomgen/xoshiro256.hpp"
+#include "time/Time.hpp"
+#include "printjson/PrintJson.hpp"
+#include "indentlog/print/tag.hpp"
+#include <signal.h>
+
+/* webserver instance */
+static xo::ref::rp<xo::web::Webserver> g_ws;
+
+void sigint_handler(int /*sig*/) {
+    std::cerr << "main thread interrupt_handler\n";
+
+    if (g_ws)
+        g_ws->interrupt_stop_webserver();
+}
+
+int
+main(int argc, char **argv) {
+    using xo::web::Webserver;
+    using xo::web::WebserverConfig;
+    using xo::json::PrintJsonSingleton;
+    using xo::vf::Volfit;
+    using xo::vf::VolfitInputCaptureSvc;
+    using xo::kalman::KalmanFilterStateExt;
+    using xo::kalman::KalmanFilterSvc;
+    using xo::kalman::KalmanFilterSpec;
+    using xo::option::FlatVolsfc;
+    using xo::option::BboTick;
+    using xo::option::StrikeSetOmd;
+    using xo::option::StrikeSetMarketModel;
+    using xo::option::UlMarketModel;
+    using xo::option::PricingContext;
+    using xo::option::OptionStrikeSet;
+    using xo::option::Secid;
+    using xo::option::Pxtick;
+    using xo::process::UpxEvent;
+    using xo::process::RealizationSource;
+    using xo::process::RealizationTracer;
+    using xo::process::StochasticProcess;
+    using xo::process::ExpProcess;
+    using xo::process::BrownianMotion;
+    using xo::sim::Simulator;
+    using xo::reactor::PtrEventStore;
+    using xo::reactor::StructEventStore;
+    using xo::reactor::ReactorSource;
+    using xo::rng::Seed;
+    using xo::rng::xoshiro256ss;
+    using xo::ref::rp;
+    using xo::time::utc_nanos;
+    using xo::time::timeutil;
+    using xo::json::PrintJsonSingleton;
+    using xo::json::PrintJson;
+    using xo::Subsystem;
+    using xo::scope;
+    using xo::xtag;
+
+    try {
+#ifdef NOT_USING
+        InitSubsys<S_option_tag>::require();
+        InitSubsys<S_process_tag>::require();
+        InitSubsys<S_reactor_tag>::require();
+#endif
+
+        XO_SUBSYSTEM_REQUIRE(volfit);
+        XO_SUBSYSTEM_REQUIRE(filter);
+        XO_SUBSYSTEM_REQUIRE(simulator);
+        XO_SUBSYSTEM_REQUIRE(process);
+
+        Subsystem::initialize_all();
+
+        signal(SIGINT, sigint_handler);
+
+        scope log(XO_ENTER0(always));
+
+        rp<PrintJson> pjson = PrintJsonSingleton::instance();
+
+        /* RC Sep 2022 - adding c++ translation of kalman/src/pywebsock/ex_websock.py;
+         *               intending to debug server segfault without complication of running
+         *               from python interpreter
+         */
+
+        Secid secid0(0, 0);
+        Secid ul0 = Secid::ul(0);
+
+        utc_nanos t0 = timeutil::ymd_hms_usec(20220926 /*ymd*/,
+                                              93000 /*hms*/,
+                                              0 /*usec*/);
+        utc_nanos t1 = t0 + std::chrono::hours(30 * 24);
+
+        /* sim = pysimulator.Simulator.make() */
+        rp<Simulator> sim = Simulator::make(t0);
+
+        /* ss = pyoption.make_option_strike_set(3, secid0, 10, 1, t1, Pxtick.penny_nickel) */
+        rp<OptionStrikeSet> ss
+            = OptionStrikeSet::regular(3 /*n*/,
+                                       secid0 /*start_id*/,
+                                       10.0 /*lo_strike*/,
+                                       1.0 /*d_strike*/,
+                                       t1 /*expiry*/,
+                                       Pxtick::penny_nickel);
+
+        /* cx = pyoption.make_pricing_context(t0, 11.11, .5, .06) */
+        rp<PricingContext> cx
+            = PricingContext::make(t0, 11.11 /*ref_spot*/,
+                                   FlatVolsfc::make(0.5) /*volatility*/,
+                                   0.06 /*rate*/);
+
+        /* TODO: replace with constant to get deterministic behavior */
+        Seed<xoshiro256ss> seed;
+
+        /* ebm = pyprocess.make_exponential_brownian_motion(t0, 11.0, 0.5) */
+        rp<ExpProcess> ebm
+            = ExpProcess::make(11.0,
+                               BrownianMotion<xoshiro256ss>::make(t0,
+                                                                  0.5 /*volatility*/,
+                                                                  seed));
+
+        /* src = pyprocess.make_realization_source(ebm, dt.timedelta(seconds=1)) */
+        rp<ReactorSource> src
+            = RealizationSource<UpxEvent, double>::make(RealizationTracer<double>::make(ebm),
+                                                        std::chrono::seconds(1));
+        src->set_name("src");
+
+        /* (A)
+         * ulm = pyoption.make_ul_market_model(ul0, cx)
+         */
+        rp<UlMarketModel> ulm = UlMarketModel::make(ul0, cx);
+        ulm->set_name("ulm");
+
+        /* (B)
+         * ssm = pyoption.make_strikeset_market_model(ss, cx)
+         */
+        rp<StrikeSetMarketModel> ssm = StrikeSetMarketModel::make(ss, cx);
+        ssm->set_name("ssm");
+
+        /* (C)
+         * ssmd = pyoption.make_strikeset_omd(ss)
+         */
+        rp<StrikeSetOmd> ssmd = StrikeSetOmd::make(ss);
+        ssmd->set_name("ssmd");
+
+        /* (D)
+         * bbos = pyoption.BboTickStore.make()
+         */
+        using BboTickStore = StructEventStore<BboTick>;
+        rp<BboTickStore> bbos = StructEventStore<BboTick>::make();
+        bbos->set_name("bbos");
+
+        /* (E)
+         * vfin = pyvolfit.make_volfit_input_capture(cx)
+         */
+        rp<VolfitInputCaptureSvc> vfin = VolfitInputCaptureSvc::make(cx);
+        vfin->set_name("vfin");
+
+        /* (F)
+         * kfspec = pyvolfit.make_kf_spec_m1(t0, s0=0.3, p0=1.0, q=5)
+         */
+        KalmanFilterSpec kfspec = Volfit::kf_spec_m1(t0, 0.3, 1.0, 5.0);
+        /* kf = pyfilter.make_kalman_filter(spec=kfspec) */
+        rp<KalmanFilterSvc> kf = KalmanFilterSvc::make(kfspec);
+        kf->set_debug_sim_flag(true);
+        kf->set_name("kf");
+
+        using KalmanFilterStateEventStore
+            = PtrEventStore<rp<KalmanFilterStateExt>>;
+
+        /* (G)
+         * kfs = pyfilter.KalmanFilterStateEventStore.make()
+         */
+        rp<KalmanFilterStateEventStore> kfs
+            = KalmanFilterStateEventStore::make();
+
+        /* sim.add_source(src) */
+        sim->add_source(src);
+
+        /* uls = pyprocess.UpxEventStore.make() */
+        using UpxEventStore = StructEventStore<UpxEvent>;
+        rp<UpxEventStore> uls = UpxEventStore::make();
+        src->attach_sink(uls);
+
+        /* (A) */
+        sim->add_source(ulm);
+        src->attach_sink(ulm);
+
+        /* (B) */
+        sim->add_source(ssm);
+        src->attach_sink(ssm);
+
+        /* (C) */
+        sim->add_source(ssmd);
+        ulm->attach_sink(ssmd);
+        ssm->attach_sink(ssmd);
+
+        /* (D) */
+        ulm->attach_sink(bbos);
+        ssm->attach_sink(bbos);
+
+        /* (E) */
+        // sim->add_source(vfin) ?
+        ssmd->attach_sink(vfin);
+
+        /* (F) */
+        // sim->add_source(kf) ?
+        vfin->attach_sink(kf);
+
+        /* (G) */
+        kf->attach_sink(kfs);
+
+        /* wconfig=pywebsock.WebserverConfig(7682, False, False, False)
+         * web=pywebsock.Webserver.make(wconfig)
+         */
+        g_ws = Webserver::make(WebserverConfig(7682 /*port*/,
+                                               false /*!tls_flag*/,
+                                               false /*!strict_host_check_flag*/,
+                                               false /*!use_retry_flag*/),
+                               PrintJsonSingleton::instance());
+
+        /* web.register_http_endpoint(uls.http_endpoint_descr("/uls")) # /dyn/uls/snap
+         * web.register_http_endpoint(kfs.http_endpoint_descr("/kfs")) # /dyn/kfs/snap
+         */
+        g_ws->register_http_endpoint(uls->http_endpoint_descr(pjson, "/uls"));
+        g_ws->register_http_endpoint(kfs->http_endpoint_descr(pjson, "/kfs"));
+
+        /* web.register_stream_endpoint(src.stream_endpoint_descr("/ws/uls"))
+         * web.register_stream_endpoint(kf.stream_endpoint_descr("/ws/kfs"))
+         */
+        g_ws->register_stream_endpoint(src->stream_endpoint_descr("/ws/uls"));
+        g_ws->register_stream_endpoint(kf->stream_endpoint_descr("/ws/kfs"));
+
+        log("starting webserver..");
+
+        g_ws->start_webserver();
+
+        log("..webserver started");
+
+        /* attempt simulation.
+         * throttle so that we have time to connect browser,  give url
+         *   http://localhost:7682/ex_websock.html
+         * pywebsock/ex_websock.py implements a governed simulation loop
+         * in python,  so that it's interruptible.
+         * here, we can rely on simulator instead
+         */
+        sim->run_throttled_until(t0 /*t1 - ignored if <= sim.t0()*/,
+                                 50 /*n_max*/,
+                                 2.5 /*replay_factor*/);
+
+
+        log("joining webserver..");
+
+        g_ws->join_webserver();
+
+        log("..joined webserver");
+    } catch (std::exception & ex) {
+        std::cerr << "caught exception" << xtag("ex", ex.what()) << std::endl;
+    }
+
+} /*main*/
+
+/* end websock_utest_main.cpp */