Question

I have this piece of code as part of a socks5 proxy server implementation. This is the part from where once the server established communication sockets with proxy client (in code – socket_) and destination server (in code clientSock_) it takes data send on a socket and exchanges it with data sent on the other socket.

I specify that this exchange happens already in a thread spawn by the server for a proxy client.

    std::size_t readable = 0;

    boost::asio::socket_base::bytes_readable command1(true);
    boost::asio::socket_base::bytes_readable command2(true);


    try 
    {
        while (1)
        {
            socket_->io_control(command1);
            clientSock_->io_control(command2);

            if ((readable = command1.get()) > 0)
            {
                transf = ba::read(*socket_, ba::buffer(data_,readable));
                ba::write(*clientSock_, ba::buffer(data_,transf));
                boost::this_thread::sleep(boost::posix_time::milliseconds(500));
            }

            if ((readable = command2.get()) > 0)
            {
                transf = ba::read(*clientSock_, ba::buffer(data_,readable));
                ba::write(*socket_, ba::buffer(data_,transf));
                boost::this_thread::sleep(boost::posix_time::milliseconds(500));
            }
        }
    }
    catch (std::exception& ex)
    {
        std::cerr << "Exception in thread while exchanging: " << ex.what() << "\n";
        return;
    }

The problem here is that I have very high CPU in the loop. Also I am not sure if here the way to know if one of the parts has closed the socket is to catch boost socket exception -> and end the data exchange.

Answer 1

The problem ca be solved by using asynchronous write/read functions. Basically use async_read_some() or async_write() – or other async functions in these categories. Also in order for async processing to work one must call io_service.run() after at least one async function was called – that will dispatch completion handler for async processing.