Simple, small, C++ embeddable webserver with WebSockets support


Seasocks - A tiny embeddable C++ HTTP and WebSocket server for Linux

CI codecov GitHub release License ConanCenter package


  • Simple C++ API
  • Serves static content from disk
  • API for building WebSocket servers
  • Simple command line binary for quick serving of static files only
  • Supports newer Hybi-10 and Hybi-16 WebSockets as well as the older Hixie style.

Stuff it doesn't do

  • It's not nearly as configurable as Apache, Lighttpd, Nginx, Jetty, etc.
  • It provides only limited support for custom content generation (e.g. Servlets).
  • It has been designed for WebSocket based control.
  • It's Linux focused and probably wont work on other systems (patches to support other systems would be welcome, but not a priority for us)

Getting started

Check out the tutorial on the wiki.

See src/app/c/ws_test.cpp for an example.

  • CMake build script updates

    CMake build script updates

    Hello! As promised after our chat at cpplang.slack#conan, a pr for better conan support. I've not (yet) looked at Windows support.

    What did I change?

    • Removed some files + added them to .gitignore
    • Added a .editorconfig file to make it easier for supported IDE's to apply formating. (See for more info)
    • Use FindPythonInterp for finding python + nicer (imho) generated embedded source (too bad btw that
    • Add a SEASOCKS_SHARED and SEASOCKS_STATIC option to build shared and static libraries together. I left the possibility for building a static library without PIC support: see seasocks_obj vs seasock_pic_obj target.
    • Small change to the internal header configuration: add @ONLY to configure to don't replace cmake type variables. This does not change anything, but is safer for the future.
    • reformatted some cmake scripts. The cmake directory is appended to the CMAKE_MODULE_PATH so some module paths can be overridden by external scripts.
    • Export the cmake targets in SeasocksTargets.cmake and generate a SeasockConfig.cmake. Also make sure to link to ZLIB::ZLIB and Threads::Threads to avoid paths of the build machine being present in the exported cmake scripts. Note that this requires a find_package(Threads REQUIRED) and find_package(ZLIB REQUIRED) in the generated SeasocksConfig.cmake.
    • Remove double quotes from arguments in add_subdirectory. No functional change. But nicer imho.
    • Copy the license on installation
    • Add a conanfile build script. This should make it easier to build seasocks on Windows. Adding a to your repo allows the master branch in-tree, without doing releases. e.g.:
      mkdir build && cd build
      conan install ..
      conan build ..

      This also works on Windows. Using MSVC, you can then simply open Visual Studio using cmake --open. Also, I made sure to not patch the sources or include conanbuildinfo.cmake in your cmake scripts.


    opened by madebr 37
  • Response getting corrupt - question

    Response getting corrupt - question

    I have written the following code (reduced and modified to the essential parts for posting here) to implement a response to a uri path "show". I want to generate a response in the code and return it. I generated this response in many different ways, but the result is always the following error.

    When I return a response string of length >=1000, the client either does not receive the payload or receives the first few characters. For all response strings of length < 1000, it has worked well. I tried to hard code the string, read it from a file, generate it programmatically etc. I tried to return as "text/plain", "application/json","text/html", but no help. It is possible that the magic number 1000 may be just a random coincidence, but it was consistent in over 30 tests I did. When I tried to do the same long responses (>1000) by modifying the example code given in "ph_test.cpp", and it has no such problem. What am I doing wrong?

    struct DataHandler : CrackedUriPageHandler {    
        DataHandler(){}; //my code has one argument for the constructor, which is irrelevant here
        virtual std::shared_ptr<Response> handle(const CrackedUri &uri,
                                                 const Request &request) override {
            std::string resp = "";
            for(int i=0; i< 999; i++) { // <= 999 is OK, but >=1000 is giving the error  
                resp += "m";
            return Response::textResponse(resp);        
    //server starting code
    auto root = make_shared<RootPageHandler>();
    auto pathHandler = make_shared<PathHandler>("show", make_shared<DataHandler>());        
    server.serve(, server_port); //server_root and server port come from elsewhere

    The response is like (where the length 1020 is correct, but the content is missing after one char):

    200 OK
    Server:  Seasocks/unversioned
    Date:  Tue, 19 Apr 2016 01:58:52 GMT
    Access-Control-Allow-Origin:  *
    Content-Length:  1,020
    Content-Type:  text/plain
    Connection:  keep-alive
    Last-Modified:  Tue, 19 Apr 2016 01:58:52 GMT
    Pragma:  no-cache
    Cache-Control:  no-store
    Expires:  Tue, 19 Apr 2016 01:58:52 GMT

    Compiler info: gcc 4.8.5 20150623 (Red Hat 4.8.5-4) CMake options: ADD_DEFINITIONS(-Wall -Wextra -pedantic -ggdb3 -fPIC)

    opened by skn2020 19
  • CMake changes

    CMake changes

    • Uses cmake BUILD_SHARED_LIBS
    • gets rid of some of the complexity previously needed to manage building both shared and static libs.
    • relies on cmake POSTIION_INDEPENDENT_CODE for those that need it
    • error on APPLE support, and take out any WIN32 other than to error about it.

    Two minor issues remain:

    • I can't get the EXPORT section to work
    • I don't know why I have to force PIC on the embedded object unconditionally.
    opened by mattgodbolt 15
  • Seasocks now compiles in Windows with c++17 and VS2019

    Seasocks now compiles in Windows with c++17 and VS2019

    I have been as careful as I can about the changes so as to hopefully not break the Linux compile. At least on WSL2 Linux, this code compiles and all tests pass.

    Build process is exactly the same for Windows (mkdir build && cdbuild followed by cmake ../) as it is in Linux; except in the resulting build directory there will be Visual Studio solution files that will enable seasocks to be built and debugged in visual studio. Please note I only tried the static library builds.


    opened by sjk7 13
  • findEmbeddedContent symbol missing

    findEmbeddedContent symbol missing

    After installing the latest version of seasocks, I'm having trouble building against libseasocks.a:

    /usr/local/lib/libseasocks.a(Connection.cpp.o): In function `seasocks::Connection::sendError(seasocks::ResponseCode, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
    Connection.cpp:(.text+0x4c2c): undefined reference to `findEmbeddedContent(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
    /usr/local/lib/libseasocks.a(Connection.cpp.o): In function `seasocks::Connection::send404()':
    Connection.cpp:(.text+0x52b5): undefined reference to `findEmbeddedContent(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
    /usr/local/lib/libseasocks.a(Connection.cpp.o): In function `seasocks::Connection::processHeaders(unsigned char*, unsigned char*)':
    Connection.cpp:(.text+0x6424): undefined reference to `findEmbeddedContent(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
    collect2: error: ld returned 1 exit status
    opened by hoytech 12
  • Some fixes

    Some fixes

    This PR replaces the source file search by file(GLOB_RECURSE …) as this is not recommended by cmake. The 2nd commit fixes some issues I encountered recently.

    opened by offa 12
  • versioned shared library

    versioned shared library

    this commit adds versioning to

    before: /usr/local/lib/ |--

    after: /usr/local/lib/ |-- -> |--

    opened by Jasper-Ben 11
  • Per-message deflate as described in RFC 7692

    Per-message deflate as described in RFC 7692

    Github issue #5

    For my work-load (somewhat redundant JSON) it reduces the transmitted message sizes to nearly 1/10th their uncompressed sizes so it will be a huge bandwidth saver.

    It basically does the bare minimum to be RFC 7692 compatible. I have tested the compression with chromium and websocketpp 0.7.0 and seasocks seems to compress/decompress messages properly in both directions.

    Current limitations:

    • Can't configure the *_no_context_takeover or *_max_window_bits extensions. It will only negotiate the default (context takeover and max window bits in both directions)
    • All transmitted messages will be compressed. Ideally you should be able to opt-out of compressing particular messages (but it does support clients that compress particular messages)
    • Only ever issues one DEFLATE block per message since the seasocks API doesn't support incremental message construction (but I believe it does support receiving multiple blocks from clients that do)
    • Various tuning parameters such as buffer size and memLevel are hard-coded. Some apps might like to customise them
    • Requires linking to zlib even if no compression will be used
    • No tests :(
    opened by hoytech 11
  • CMake added

    CMake added

    This PR addes cmake as a second build tool.


    • Building of library and apps
    • Installation using make install
    • Travis CI (Matrix using both)
    • Generation of embedded content
    • Testing compiler for emplace()
    • Optional building / running of tests using gtest / gmock (default: OFF)
    • Configure file - Config.h (based on a custom template in cmake/)

    Not (yet) available:

    • Building tests on CI using cmake

    Since google has merged gtest / gmock into one project - gmock depends on gtest though - i'm not sure how to handle this case on CI. It seems gmock requires gtest but doesn't ship it anymore in one bundle (?).

    At the moment cmake will look for both if tests are enabled, otherwise there's no dependency on gtest / gmock if disabled.

    What's different to autoconf:

    The cmake builds will use it's own Config.h (cmake directory); it has only a definition for HAVE_UNORDERED_MAP_EMPLACE, since i didn't see any usage of all the other flags. However, adding more options is simple enough.

    opened by offa 11
  • Some code related questions

    Some code related questions

    I have some code related questions:

    1. Is the -ggdb3 flag still necessary? It's enabled for all build types; but mainly debug related (correct?).
    2. Are the compiler checks for map::emplace() and override still necessary? Any C++11 conform compiler should support thesei).

    i) The test for <atomic> isn't affected by this, as it still serves a valid reason – eg. some embedded systems may not support it.

    opened by offa 10
  • Multipart responses

    Multipart responses

    I've been enjoying using seasocks for websocket content.

    I want to stream mjpegs from seasocks. To do this, I need to send a multipart http response. Seasocks looks like it really wants you to generate the entire page response and then it will send that all at once. Is there a way to send a multipart response (where the response comes back in chunks spread out over time)? I don't see it from the interface provided for the response.

    opened by AustinSchuh 10
  • Test migration to Catch 3.x

    Test migration to Catch 3.x

    How about migrating tests to Catch 3.x, the latest version?

    v3 is the next major version of Catch2 and brings three significant changes:

    • Catch2 is now split into multiple headers
    • Catch2 is now compiled as a static library
    • C++14 is the minimum required C++ version

    Since it's no longer header-only we need some other way to consume it though. Eg. using Conan and/or as precondition?

    opened by offa 0
  • Static link seasocks

    Static link seasocks

    Hi, how can I static link seasocks? I did not found anything on the documentation..

    I have tried this: LIBRARIES = -lm /home/user/seasocks/build/src/main/c/libseasocks.a

    but getting these errors:

    /usr/bin/ld: /home/user/seasocks/build/src/main/c/libseasocks.a(Server.cpp.o): relocation R_X86_64_PC32 against symbol `_ZTVN8seasocks6ServerE' can not be used when making a shared object; recompile with -fPIC
    /usr/bin/ld: final link failed: bad value
    collect2: error: ld returned 1 exit status

    I suppose there is an extra step when I'm building seasocks?

    opened by toutriste 1
  • Conan center build 1.4.5 failed

    Conan center build 1.4.5 failed

    A simple upgrade failed:

    See more info at:

    opened by mattgodbolt 12
  • v1.4.5(Aug 28, 2022)

    A refresh update with latest code and changes.

    • Support for many different versions of Clang
    • Various error handling fixes (thanks @staz), one fewer platform dependency
    • CMake versioned shared libraries
    • Windows (!) support - thanks @sjk7 and @madebr
    Source code(tar.gz)
    Source code(zip)
  • v1.4.4(Aug 7, 2020)

  • v1.4.3(Jan 24, 2020)

  • v1.4.2(Apr 15, 2019)

  • v1.4.1(Oct 8, 2018)

    • Requires C++14.
    • Support for Python 3 in build process.
    • Various CMake improvements.
    • Internal improvements to better use smart pointers, and to take advantage of C++14 features.
    • Fix to CMake build process (plays better with Conan)
    Source code(tar.gz)
    Source code(zip)
  • v1.3.2(Sep 9, 2017)

    Seasock supports latest GCC 7 and Clang 5 compiler now. SONAME is available through CMake and Catch uses v1.10 which notable reduces the test runtime.


    Development is going to upgrade to C++14 from v1.4.x onwards.

    Source code(tar.gz)
    Source code(zip)
  • v1.3.1(Apr 26, 2017)

    In 1.3.0 we added streaming, which introduced a dependency on libz. For those who don't want this dependency, in this release configuring with -DDEFLATE_SUPPORT=Off will drop the dependency.

    Source code(tar.gz)
    Source code(zip)
  • v1.3.0(Mar 23, 2017)

  • v1.2.6(Jan 18, 2017)

    Added the ability to change the buffer size used for clients.

    Internal fixes to make CMake builds more consistent.

    Enums are now enum classes: apologies for the API change. I suck at semantic versioning, it turns out :(

    Source code(tar.gz)
    Source code(zip)
  • v1.2.4(Mar 16, 2016)

  • v1.2.2(Mar 7, 2016)

  • v1.2.1(Mar 6, 2016)

  • v1.2.0(Mar 6, 2016)

    New asynchronous interface allows handlers to defer sending their replies until they're ready. This also makes streaming possible.

    If you have custom Responses and don't want to change them, consider deriving them from SynchronousResponse.

    The async_test example in src/apps/c will give some idea of how asynchronous responses should be performed.

    Source code(tar.gz)
    Source code(zip)
  • v1.1.6(Sep 28, 2015)

  • v1.1.5(May 27, 2015)

    A minor release that fixes the slightly weird behaviour of split() in StringUtil which returned {""} for splitting an empty string instead of {}.

    This has a knock-on effect for the CrackedUriPageHandler: now the "/" handler will have an empty path instead of a single empty element.

    Source code(tar.gz)
    Source code(zip)
  • v1.1.2(Oct 27, 2014)

    A fix for Firefox: isupport websocket upgrade "Connection:" header with comma-separated values. Previously prevented Firefox from talking to websockets.

    Source code(tar.gz)
    Source code(zip)
  • v1.1.1(Jul 24, 2014)

    Fixes in the JSON code:

    • jsonToStream is now available for user objects: define a member function void jsonToStream(std::ostream &); and stream out your contents.
    • Array and map generation for container types now need to be explicitly called out with makeMapFromContainer and makeArrayFromContainer. They work on all container and map types now too.
    Source code(tar.gz)
    Source code(zip)
  • v1.0.1(Apr 15, 2014)

  • v1.0(Mar 27, 2014)

  • v0.1(Oct 15, 2013)

Matt Godbolt
Compiler Explorer and jsbeeb creator, ex-Google, ex-games, ex-trading chap.
Matt Godbolt
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