Question

i have a problems with ASIO boost library. The problem are asynchronous functions.

This is simple server code.

void handle_accept( const boost::system::error_code& error )
{
    std::cout << "Someone connected" << std::endl;
}

void handle_read( const boost::system::error_code& error )
{
    printf( "Message: %s \n", somedata);
}

int main()
{

std::cout << "Starting server ....\n" << std::endl;

try
{
    boost::asio::io_service io_service;
    tcp::socket  mysocket(io_service);
    tcp::acceptor myacceptor(io_service, tcp::endpoint(tcp::v4(), 5000));

    myacceptor.async_accept( mysocket, boost::bind( &handle_accept, boost::asio::placeholders::error));
    mysocket.async_receive(  boost::asio::buffer(somedata, 1024)  , boost::bind( &handle_read, boost::asio::placeholders::error) );
    io_service.run();

    std::cout << "END. \n" << std::endl;
    sleep(5);

}  catch (std::exception& e)
{
  std::cerr << "Exception: " << e.what() << "\n";
}
return 0;

}

and client code here

int main()
{
std::cout << "Starting client ....\n" << std::endl;

try
{
boost::asio::io_service io_service;

tcp::resolver resolver(io_service);
tcp::resolver::query query(tcp::v4(), "localhost", "5000");
tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);
tcp::socket mysocket(io_service);

boost::asio::connect(mysocket, endpoint_iterator);

sleep(5);
sprintf( somedata, "This is a message i sent.");
mysocket.send( boost::asio::buffer(somedata, 1024)  );

}  catch (std::exception& e)
{
  std::cerr << "Exception: " << e.what() << "\n";
}
return 0;
}

So, How it should work. Server should wait on connection from client, when client is connected, it should call handle_accept. When client is connected, handle_accept is really called, but it also calls handle_read even no data is recieved !!! why ? client sends data after 5 seconds after making connection.

thank you very much.

Answer 1

The receive completes immediately because it cannot wait because it has nothing to wait for. No data will ever be received on a TCP listening socket. Call async_receive on your connected sockets only.