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AutobahnC++

WAMP for C++ on Boost/ASIO.

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Introduction

AutobahnC++ is a subproject of Autobahn which provides a C++ WAMP implementation that is able to talk WAMP over stdio pipes.

  • Caller
  • Callee
  • Publisher
  • Subscriber

AutobahnC++ is open-source, licensed under the Boost Software License.

The API and implementation make use of modern C++ 11 and new asynchronous idioms using (upcoming) features of the standard C++ library, in particular Futures, Continuations and Lambdas.

Continuations are one way of managing control flow in an asynchronous program. Other styles include: asynchronous Callbacks, Coroutines (yield or await), Actors (Erlang/OTP, Scala/Akka or Rust) and Transactional memory.

AutobahnC++ supports running WAMP (rawsocket-msgpack) over TCP(-TLS), Unix domain sockets or pipes (stdio). The library is "header-only", light-weight (< 2k code lines) and depends on the following:

For getting help, questions or feedback, get in touch on the mailing list, Twitter or IRC #autobahn (Freenode).

Show me some code!

Here is how programming with C++ and AutobahnC++ looks like.

Calling a remote Procedure

auto c1 = session.call("com.mathservice.add2", std::make_tuple(23, 777))
    .then([&](boost::future<wamp_call_result> result) {
        std::cout << "Got call result " << result.get().argument<uint64_t>(0) << std::endl;
    });

Registering a remoted Procedure

auto r1 = session.provide("com.myapp.cpp.square",
    [](autobahn::wamp_invocation invocation) {
        std::cout << "Procedure is invoked .." << endl;
        uint64_t x = invocation->argument<uint64_t>(0);
        return x * x;
    })
    .then([](boost::future<autobahn::wamp_registration> reg) {
        std::cout << "Registered with ID " << reg.get().id() << std::endl;
    });

Publishing an Event

session.publish("com.myapp.topic2", std::make_tuple(23, true, std::string("hello")));

Publishing an Event (acknowledged)

auto opts = PublishOptions();
opts.acknowledge = True;

session.publish("com.myapp.topic2", std::make_tuple(23, true, std::string("hello")), opts)
    .then([](boost::future<autobahn::wamp_publication> pub) {
        std::cout << "Published with ID " << pub.get().id() << std::endl;
    });

Subscribing to a Topic

auto s1 = session.subscribe("com.myapp.topic1",
    [](const autobahn::wamp_event& event) {
        std::cout << "Got event: " << event.argument<uint64_t>(0) << std::endl;
    })
    .then([](boost::future<autobahn::wamp_subscription> sub) {
        std::cout << "Subscribed with ID " << sub.get().id() << std::endl;
    });

Here is JavaScript running in Chrome call into C++ running on command line. Both are connected via a WAMP router, in this case Autobahn|Python based.

Installation

Autobahn C++ is a "header-only" library, which means there isn't anything to build (for the library itself), and the only thing to install are the header files.

For using Autobahn C++ in your project, clone the project, checkout a Git release tag (optional) and copy the library header files to your system (or project include directory):

cd ~
git clone https://github.com/crossbario/autobahn-cpp.git
cd autobahn-cpp
cp -r autobahn/ /usr/local/include/

Examples

The Autobahn C++ repository contains a number of examples that demonstrate all 4 basic patterns of using WAMP.

There are also examples for WAMP-CRA and Unix domain sockets.

Building dependencies

The instructions below were tested on Debian/Ubuntu and build and install the following:

  • Boost in /opt/boost
  • MsgPack-C in /opt/msgpackc
  • WebSocketC++ in /opt/websocketpp
  • AutobahnC++ in /opt/autobahncpp

Notes

  • The library code is written in standard C++ 11. Target toolchains currently include clang and gcc. Support for MSVC is tracked on this issue.
  • While C++ 11 includes std::future in the standard library, this lacks continuations. boost::future.then allows attaching continuations to futures as outlined in the proposal here. This feature will come to standard C++, but probably not before 2017 (see C++ Standardisation Roadmap)
  • Support for when_all and when_any as described in above proposal depends on Boost 1.56 or higher.
  • The library and example programs were tested and developed with clang 3.4, libc++ and Boost trunk/1.56 on an Ubuntu 13.10 x86-64 bit system. It also works with gcc 4.8, libstdc++ and Boost trunk/1.56. Your mileage with other versions of the former may vary, but we accept PRs;)

System libraries and cmake

Install some libs and build tools (these are for Debian/Ubuntu):

sudo apt-get install -y libbz2-dev libssl-dev

Install cmake

cd ~
wget https://cmake.org/files/v3.11/cmake-3.11.0-Linux-x86_64.sh
chmod +x cmake-3.11.0-Linux-x86_64.sh
sudo ./cmake-3.11.0-Linux-x86_64.sh --prefix=/opt
sudo mv /opt/cmake-3.11.0-Linux-x86_64 /opt/cmake

Clang (alternative)

If you want to work with Clang (rather than GCC), install clang and libc++ (these are for Ubuntu):

sudo apt-get install -y clang libc++1 libc++-dev

Then make Clang available:

$ sudo update-alternatives --config c++
There are 2 choices for the alternative c++ (providing /usr/bin/c++).

  Selection    Path                      Priority   Status
------------------------------------------------------------
* 0            /usr/bin/g++              20        auto mode
  1            /usr/bin/clang++          10        manual mode
  2            /usr/bin/clang++-libc++   5         manual mode
  3            /usr/bin/g++              20        manual mode

Press <enter> to keep the current choice[*], or type selection number: 1
update-alternatives: using /usr/bin/clang++ to provide /usr/bin/c++ (c++) in manual mode

Boost

Most of the time, your distro's Boost libraries will be outdated (unless you're using Arch or Homebrew). Don't waste time with those. To build the latest Boost 1.66 (current release as of 2018/4) from sources.

Get Boost:

cd ~
wget https://dl.bintray.com/boostorg/release/1.66.0/source/boost_1_66_0.tar.bz2
tar xvjf boost_1_66_0.tar.bz2
cd boost_1_66_0

Then, to build using the GCC toolchain:

./bootstrap.sh --with-toolset=gcc
./b2 toolset=gcc -j4
sudo ./b2 install --prefix=/opt/boost

Note: The -j 4 option will allow use of 4 CPU cores for building.

Instead, to build using the Clang toolchain:

./bootstrap.sh --with-toolset=clang
./b2 toolset=clang -j4 \
    cxxflags="-stdlib=libc++" linkflags="-stdlib=libc++"
sudo ./b2 install --prefix=/opt/boost

Then add the following to your ~/.profile or ~/.bashrc:

export BOOST_ROOT=/opt/boost
export LD_LIBRARY_PATH=${BOOST_ROOT}/lib:${LD_LIBRARY_PATH}

MsgPack-C

Get MsgPack-C and install:

cd ~
git clone https://github.com/msgpack/msgpack-c.git
cd msgpack-c
git checkout cpp-1.4.2
cmake -DMSGPACK_CXX11=ON -DCMAKE_INSTALL_PREFIX=/opt/msgpack .
make
sudo make install

On FreeBSD, you need to pkg install autotools and invoke gmake instead of make.

Then add the following to your ~/.profile or ~/.bashrc:

export MSGPACK_ROOT=/opt/msgpack
export LD_LIBRARY_PATH=${MSGPACK_ROOT}/lib:${LD_LIBRARY_PATH}

WebSocket++

Get WebSocket++ and install:

cd ~
git clone https://github.com/zaphoyd/websocketpp.git
cd websocketpp
cmake -DCMAKE_INSTALL_PREFIX=/opt/websocketpp .
sudo make install

Then add the following to your ~/.profile or ~/.bashrc:

export WEBSOCKETPP_ROOT=/opt/websocketpp
export LD_LIBRARY_PATH=${WEBSOCKETPP_ROOT}/lib:${LD_LIBRARY_PATH}

Building the examples

Now that we have all the dependencies, to build the examples:

mkdir build
cd build
/opt/cmake/bin/cmake ..
make -j4
sudo make install

You should see a clean build like in the following output:

oberstet@thinkpad-t430s:~/scm/crossbario/autobahn-cpp/build$ /opt/cmake/bin/cmake ..
-- The C compiler identification is GNU 5.4.0
-- The CXX compiler identification is GNU 5.4.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Looking for pthread.h
-- Looking for pthread.h - found
-- Looking for pthread_create
-- Looking for pthread_create - not found
-- Looking for pthread_create in pthreads
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - found
-- Found Threads: TRUE
-- Boost version: 1.66.0
-- Found the following Boost libraries:
--   program_options
--   system
--   thread
--   random
--   chrono
--   date_time
--   atomic
-- Found OpenSSL: /usr/lib/x86_64-linux-gnu/libcrypto.so (found version "1.0.2g")
-- AUTOBAHN_BUILD_EXAMPLES:  ON
-- CMAKE_ROOT:               /opt/cmake/share/cmake-3.11
-- Boost_INCLUDE_DIRS:       /opt/boost/include
-- Boost_LIBRARIES:          /opt/boost/lib/libboost_program_options.so/opt/boost/lib/libboost_system.so/opt/boost/lib/libboost_thread.so/opt/boost/lib/libboost_random.so/opt/boost/lib/libboost_chrono.so/opt/boost/lib/libboost_date_time.so/opt/boost/lib/libboost_atomic.so
-- Msgpack_INCLUDE_DIRS:     /opt/msgpack/include
-- Msgpack_LIBRARIES:        /opt/msgpack/libs
-- Websocketpp_INCLUDE_DIRS: /opt/websocketpp/include
-- Websocketpp_LIBRARIES:    /opt/websocketpp/libs
-- Configuring done
-- Generating done
-- Build files have been written to: /home/oberstet/scm/crossbario/autobahn-cpp/build
oberstet@thinkpad-t430s:~/scm/crossbario/autobahn-cpp/build$ make -j4
Scanning dependencies of target examples_parameters
[  5%] Building CXX object examples/CMakeFiles/examples_parameters.dir/parameters.cpp.o
[ 11%] Linking CXX static library libexamples_parameters.a
[ 11%] Built target examples_parameters
Scanning dependencies of target callee
Scanning dependencies of target caller
Scanning dependencies of target provide_prefix
Scanning dependencies of target wampcra
[ 16%] Building CXX object examples/CMakeFiles/caller.dir/caller.cpp.o
[ 22%] Building CXX object examples/CMakeFiles/callee.dir/callee.cpp.o
[ 27%] Building CXX object examples/CMakeFiles/provide_prefix.dir/callee.cpp.o
[ 33%] Building CXX object examples/CMakeFiles/wampcra.dir/wampcra.cpp.o
[ 38%] Linking CXX executable wampcra
[ 38%] Built target wampcra
Scanning dependencies of target subscriber
[ 44%] Linking CXX executable caller
[ 50%] Building CXX object examples/CMakeFiles/subscriber.dir/subscriber.cpp.o
[ 50%] Built target caller
Scanning dependencies of target uds
[ 55%] Linking CXX executable callee
[ 61%] Linking CXX executable provide_prefix
[ 66%] Building CXX object examples/CMakeFiles/uds.dir/uds.cpp.o
[ 66%] Built target callee
Scanning dependencies of target publisher
[ 66%] Built target provide_prefix
Scanning dependencies of target websocket_callee
[ 72%] Building CXX object examples/CMakeFiles/publisher.dir/publisher.cpp.o
[ 77%] Building CXX object examples/CMakeFiles/websocket_callee.dir/websocket_callee.cpp.o
[ 83%] Linking CXX executable subscriber
[ 83%] Built target subscriber
[ 88%] Linking CXX executable publisher
[ 94%] Linking CXX executable uds
[ 94%] Built target publisher
[ 94%] Built target uds
[100%] Linking CXX executable websocket_callee
[100%] Built target websocket_callee
oberstet@thinkpad-t430s:~/scm/crossbario/autobahn-cpp/build$

And here are some details for one of the built example binaries:

oberstet@thinkpad-t430s:~/scm/crossbario/autobahn-cpp/build$ file examples/websocket_callee
examples/websocket_callee: ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=bfcab40b2350acd5869d913226723999cf0b822e, not stripped
oberstet@thinkpad-t430s:~/scm/crossbario/autobahn-cpp/build$ ldd examples/websocket_callee
    linux-vdso.so.1 =>  (0x00007fff44760000)
    libboost_program_options.so.1.66.0 => /opt/boost/lib/libboost_program_options.so.1.66.0 (0x00007f8518873000)
    libboost_system.so.1.66.0 => /opt/boost/lib/libboost_system.so.1.66.0 (0x00007f851866f000)
    libboost_thread.so.1.66.0 => /opt/boost/lib/libboost_thread.so.1.66.0 (0x00007f8518446000)
    libssl.so.1.0.0 => /lib/x86_64-linux-gnu/libssl.so.1.0.0 (0x00007f85181dd000)
    libcrypto.so.1.0.0 => /lib/x86_64-linux-gnu/libcrypto.so.1.0.0 (0x00007f8517d99000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f8517b7c000)
    libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f85177fa000)
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f85175e4000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f851721a000)
    librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f8517012000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f8516e0e000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f8518af3000)
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f8516b05000)
oberstet@thinkpad-t430s:~/scm/crossbario/autobahn-cpp/build$

Resources

Closures Cheatsheet

  • [] Capture nothing (or, a scorched earth strategy?)
  • [&] Capture any referenced variable by reference
  • [=] Capture any referenced variable by making a copy
  • [=, &foo] Capture any referenced variable by making a copy, but capture variable foo by reference
  • [bar] Capture bar by making a copy; don't copy anything else
  • [this] Capture the this pointer of the enclosing class

Release process

To push a new release of the toolchain Docker image:

git tag -a v20.8.1 -m "tagged release"
source docker/versions.sh
make build_gcc
make publish_gcc

Note: clang is currently broken.

About

WAMP for C++ in Boost/Asio

crossbar.io/autobahn

Topics

real-time boost pubsub rpc asio wamp autobahn

Resources

Readme

License

BSL-1.0 license
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