wampcc is C library that implements the Web Application Messaging Protocol (WAMP).

wampcc provides the WAMP basic profile for client roles and also a lightweight implementation of a WAMP router / dealer.

Features

• Builds on: Linux, Windows (Visual Studio) & Mac OS 10
• Roles: Caller, Callee, Subscriber, Publisher, Dealer, Router
• Message serializations: JSON, MessagePack
• Transports: TCP using raw-socket and web-socket
• SSL/TLS supported for both client and server sessions
• Uses modern C
• Extensively tested
• Permissive license (MIT)

Dependencies

wampcc aims to depend mostly on C libraries, making it easier to build and work on a range of platforms.

• libuv (network IO)
• jansson (JSON encode & decode)
• http-parser
• OpenSSL
• websocketpp -- C header only
• msgpack-c -- C header only
• Modern C compiler, GNU autotools (Linux), CMake (Linux & Windows)

Here is what programming with wampcc looks like.

Establishing a WAMP session

Before a WAMP session can be established, a tcp_socket has to be created and connected to a WAMP router / dealer server.

After the socket is successfully connected it is used to construct a wamp_session. Next the HELLO sequence is initiated to establish the logical WAMP session.

All wampcc objects make use of a shared kernel object, which provides threads for event handling and socket IO.

/* Create the wampcc kernel. */

kernel the_kernel;

/* Create the TCP socket and attempt to connect. */

std::unique_ptr<tcp_socket> socket(new tcp_socket(&the_kernel));
socket->connect("127.0.0.1", 55555).wait_for(std::chrono::seconds(3));

if (!socket->is_connected())
  throw std::runtime_error("connect failed");

/* With the connected socket, create a wamp session & logon to the realm
 * called 'default_realm'. */

auto session = wamp_session::create<websocket_protocol>(
  &the_kernel, std::move(socket));

session->hello("default_realm").wait_for(std::chrono::seconds(3));

if (!session->is_open())
  throw std::runtime_error("realm logon failed");

Calling a remote procedure

C lambda functions are used to handle the asynchronous result of a call request, and this usage pattern is the same for other kinds of request.

This example shows a request to call a remote procedure named math.service.add with arguments 100 & 200.

session->call("math.service.add", {}, {{100, 200}, {}},
              [](wampcc::wamp_session&, wampcc::result_info result) {
                if (result)
                  std::cout << "got result: " << result.args.args_list[0] << std::endl;
              });

Registering a remote procedure

session->provide("math.service.add", {},
                 [](wamp_session&, registered_info info) {
                   if (info)
                     std::cout << "procedure registered with id "
                               << info.registration_id << std::endl;
                   else
                     std::cout << "procedure registration failed, error "
                               << info.error_uri << std::endl;
                 },
                 [](wamp_session& ws, invocation_info info) {
                   int total = 0;
                   for (auto& item : info.args.args_list)
                     if (item.is_int())
                       total  = item.as_int();
                   ws.yield(info.request_id, {total});
                 });

Subscribing to a topic

session->subscribe("random_number", {},
                   [](wampcc::wamp_session&, subscribed_info info) {
                     std::cout << "subscribed "
                               << (info ? "ok" : "failed")
                               << std::endl;
                   },
                   [](wampcc::wamp_session&, event_info info) {
                     for (auto& x : info.args.args_list)
                       std::cout << "got update: " << x << " ";
                     std::cout << std::endl;
                   });

Publishing to a topic

int random_variable = std::rand();
session->publish("random_number", {}, {{random_variable}, {}});

Terminating a session

A thread can wait for a wamp_session to be remotely closed by waiting on an appropriate std::future. A wamp_session that is no longer needed must be closed and the closure operation completed before it can be deleted.

session->closed_future().wait_for(std::chrono::minutes(10));
session->close().wait();

Embedding a wamp router

An embedded wamp router is provided by creating a wamp_router object.

wamp_router router(&the_kernel);

It is instructed to begin listening on a particular port for new clients, together with the policy to use for authentication.

/* Accept clients on IPv4 port, without authentication. */

auto fut = router.listen(auth_provider::no_auth_required(), 55555);

if (auto ec = fut.get())
  throw runtime_error(ec.message());

An individual RPC is provided by defining the realm & name through which it can be called by a WAMP session, together with the lambda function which does the actual work of generating a call result.

router.callable(
  "default_realm", "greeting",
  [](wamp_router&, wamp_session& caller, call_info info) {
    caller.result(info.request_id, {"hello"});
  });

The complete listing for these examples can be found at:

• demo_embedded_router.cc
• demo_client.cc

Building wampcc involves several steps, including: installation of build tools; building the dependent libraries; obtaining the source; and source configuration.

Setting up build tools

wampcc can be built on Linux using either autotools, or cmake. The latter is particularly useful for integration with IDE's, such as clion.

Building on Linux presumes that some essential programs are available, including:

• git
• autoconf (if using autotools approach)
• cmake (if using cmake approach)
• g
• make
• wget
• libtool
• libssl headers & libraries

wampcc was developed on xubuntu and on this system these tools can be installed using the command:

sudo apt-get install cmake git autoconf gcc g   make wget libtool libssl-dev

Building dependent libraries

wampcc requires that the C libraries libuv and jansson have already been built and installed. The location of these libraries must be provided during the wampcc source configuration step.

Obtaining the source

The latest version of wampcc can be downloaded from github using:

git clone https://github.com/darrenjs/wampcc.git

This will fetch the source files directly from github and place them in a folder named wampcc/.

Some third party code is directly integrated into wampcc, and are compiled alongside wampcc source code. For convenience these are stored in the 3rdparty folder; no additional download step is required to obtain them.

Autotools approach

Taking the autotools approach, if building from the git sources the configure script must be first generated. An included helper script can do this:

./scripts/autotools_setup.sh

The source code is now ready to be configured. This is done by running the configure script, and passing it the locations of libuv and jansson, and also the location where wampcc should finally be installed.

./configure  --prefix=/var/tmp/wampcc_install  --with-libuv=/opt/libuv-1.10.2 --with-jansson=/opt/jansson-2.10

Note that the locations of libuv and jansson will be specific to your host, and will unlikely match this example.

Finally the build and install steps are run:

make install

If all goes well wampcc will be installed into the prefix location.

CMake approach

wampcc can also be built using cmake. The following instructions show how to use cmake to set up a command line build.

The preferred approach is to create a separate build folder outside of the source tree. In this example the build folder is /var/tmp/wmampcc_cmake_build.

mkdir -p /var/tmp/wmampcc_cmake_build
cd /var/tmp/wmampcc_cmake_build

Next is the invocation of the cmake program to generate the makefiles. This tells cmake where to find the libuv and jansson libraries, where to install the built targets, and where to find the wampcc source. The paths in this example need to be replaced with paths specific to your system. This command should be invoked from within the build folder.

cmake --verbose \
-DCMAKE_VERBOSE_MAKEFILE:BOOL=ON \
-DCMAKE_BUILD_TYPE=Release \
-DLIBUV_DIR=/opt/libuv-1.10.2 \
-DJANSSON_DIR=/opt/jansson-2.10 \
-DCMAKE_INSTALL_PREFIX=/var/tmp/wampcc_install \
/var/tmp/wampcc_src

If libuv and jansson are already installed on your system, rather than being separately built and provided, cmake can instead be configured to find and use them, simply by omitting the corresponding variables:

cmake -DCMAKE_INSTALL_PREFIX=/var/tmp/wampcc_install /var/tmp/wampcc_src

Following successful generation of the make files, wampcc can be built using make:

make

The following steps assume that you wish to install wampcc and the required dependencies in C:\build. You may modify this by replacing C:\build with the path of your choice.

The dependecies are build in Release and wampcc in Debug. You may change these by modifying the -DCMAKE_BUILD_TYPE CMake argument.

It's assumed that you are using Visual Studio and have NMake installed (which comes with Visual Studio). Visual Studio also optionally comes with CMake (this is called 'CMake Tools for Visual Studio'). However, this tends to be out-dated and it is recommened that you use the latest version of CMake. If you do have CMake Tools for Visual Studio installed, then you should run the latest version of CMake by invoking C:\Program Files\CMake\bin\cmake.exe instead of plain cmake in the commands below.

This step compiles and sets up the dependencies.

1. Download and install CMake.

2. Download and install OpenSSL, including the headers. Here is a good source of compiled binaries.

3. Download and unzip jansson and libuv source files.

4. Run the correct Visual Studio developer command prompt for the architecture (e.g. x86/x64) that you are compiling for. The architecture must match that of the OpenSSL libraries that you just installed.

   For example, if you installed the 64-bit version of OpenSSL and are using Visual Studio 2017, then you must use 'x64 Native Tools Command Prompt for VS2017'. This should be available from the Visual Studio folder in the Start menu.

5. Go inside the jansson source folder, and run:

   mkdir build
   cd build
   cmake -G "NMake Makefiles" -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=C:\build\jansson ..
   nmake
   nmake install
   

6. Go inside the libuv source folder, and run:

   mkdir build
   cd build
   cmake -G "NMake Makefiles" -DCMAKE_BUILD_TYPE=Release ..
   nmake
   mkdir C:\build\libuv
   mkdir C:\build\libuv\lib
   copy uv.dll C:\build\libuv\lib
   copy uv.lib C:\build\libuv\lib
   mkdir C:\build\libuv\include
   xcopy /E ..\include C:\build\libuv\include
   

   Note that libuv does not provide an install target, hence why we had to manually copy the files over.

1. Download a copy of wampcc

2. Run Visual Studio command line tools as described in the previous section

3. Run

   mkdir build
   cd build
   cmake -G "NMake Makefiles" -DCMAKE_BUILD_TYPE=Debug -DCMAKE_INSTALL_PREFIX=C:\build\wampcc -DJANSSON_DIR=C:\build\jansson -DLIBUV_DIR=c:\build\libuv  -DOPENSSL_ROOT_DIR="C:\Program Files\OpenSSL-Win64" ..
   nmake
   

   If the paths to libuv, jansson or OpenSSL are different then you will need to change the appropriate parameters in the command above.

4. If you wish to install wampcc, you can do so:

   nmake install