Question

I’m developing a 3d (first/third person) game and I’m trying to make it multiplayer using TCP sockets. I’m using the boost asio library for this, and I’m in a little over my head. I’ve played with the tutorials and examples a bit on the boost asio doc page and they compiled/ran/worked just fine, I’m just a little confused as to how everything works.

Right now I’m just trying to make the server accept messages from the client, and print the message after receiving it. When I execute the code below (it compiles/links/runs fine), nothing happens. More specifically, the client appears to successfully send the message, and the server never seems to receive the message.

Client code:

ClientFramework::ClientFramework() :
    mResolver(mIOService)
{
}

bool ClientFramework::Initialize()
{
    try
    {
        tcp::resolver::query query("localhost", "daytime");
        tcp::resolver::iterator it = mResolver.resolve(query);
        tcp::socket socket(mIOService);
        boost::asio::connect(socket, it);

        std::string s = "hello world";
        boost::system::error_code e;
        socket.write_some(boost::asio::buffer(s.c_str(), s.size()), e);

        if (e)
        {
            throw boost::system::system_error(e);
        }
    } catch (std::exception& e)
    {
        gLog << LOG_ERROR << e.what() << "\n";
    }

    return true;
}

Server code:

ServerFramework::ServerFramework() :
    mAcceptor(mIOService, tcp::endpoint(tcp::v4(), 13))
{
}

bool ServerFramework::Initialize()
{
    mIOService.run();
    StartAccept();

    return true;
}

void ServerFramework::StartAccept()
{
    Connection::ptr conn =
        Connection::create(mAcceptor.get_io_service());
    mAcceptor.async_accept(conn->Socket(),
        boost::bind(&ServerFramework::HandleAccept, this, conn,
            boost::asio::placeholders::error));
}

void ServerFramework::HandleAccept(Connection::ptr conn,
    const boost::system::error_code& error)
{
    if (!error)
    {
        conn->Initialize();
    }

    StartAccept();
}

Connection::ptr Connection::create(boost::asio::io_service& io_service)
{
    return ptr(new Connection(io_service));
}

tcp::socket& Connection::Socket()
{
    return mSocket;
}

void Connection::Initialize()
{
    boost::asio::async_read(mSocket, boost::asio::buffer(buf, BUFFER_SIZE),
        boost::bind(&Connection::handle_read, shared_from_this(),
          boost::asio::placeholders::error,
          boost::asio::placeholders::bytes_transferred));
}

Connection::Connection(boost::asio::io_service& io_service) :
    mSocket(io_service)
{
}

void Connection::handle_read(const boost::system::error_code& e, size_t size)
{
    std::string s(buf, size);
    gLog << LOG_INFO << s << "\n";

    boost::asio::async_read(mSocket, boost::asio::buffer(buf, BUFFER_SIZE),
        boost::bind(&Connection::handle_read, shared_from_this(),
          boost::asio::placeholders::error,
          boost::asio::placeholders::bytes_transferred));
}

Answer 1

It does not look like your io_service has any work to do when you invoke run().

bool ServerFramework::Initialize()
{
    mIOService.run(); // <-- you don't check the return value here
    StartAccept();

    return true;
}

it will return the number of handlers executed, I suspect it is zero. Try invoking it after async_accept()

bool ServerFramework::Initialize()
{
    StartAccept();
    mIOService.run();

    return true;
}

Though, it isn’t entirely obvious by your limited code snippets where you invoke ServerFramework::Initialize(). I suggest editing your question with a short, self contained, correct example that we can compile with little to no effort. Your current code will not compile without additional boilerplate stuff, like main().