Boost.asio server-client. Connect between 2 computers

Question

Im following the tutorials at the boost official web site http://www.boost.org/doc/libs/1_55_0/doc/html/boost_asio/tutorial/tutdaytime1.html.

The program is working perfectly if i connect to "localhost" or "127.0.0.1" on the same machine. But if i run the client on another computer with the same network it fails to connect to the server. Why is this happening? and what would i have to do to get the client to run on another network?

Error: connect: No connection could be made because the target machine actively refused it.

Client:

#include <iostream>
#include <boost/array.hpp>
#include <boost/asio.hpp>

using boost::asio::ip::tcp;

int main()
{
    try
    {
        boost::asio::io_service io_service;

        tcp::resolver resolver(io_service);

        char* serverName = "localhost";
        tcp::resolver::query query(serverName, "daytime");
        tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);

        tcp::socket socket(io_service);
        while(true)
        {
            boost::asio::connect(socket, endpoint_iterator);

            for (;;)
            {
                boost::array<char, 128> buf;
                boost::system::error_code error;

                size_t len = socket.read_some(boost::asio::buffer(buf), error);

                if (error == boost::asio::error::eof)
                    break; // Connection closed cleanly by peer.
                else if (error)
                    throw boost::system::system_error(error); // Some other error.

                std::cout.write(buf.data(), len);
                std::cout <<"\n";
            }
        }
    }
    catch (std::exception& e)
    {
        std::cerr << e.what() << std::endl;
    }

    return 0;
}

Server:

#include <iostream>
#include <string>
#include <boost/asio.hpp>

using boost::asio::ip::tcp;

int main()
{
    try
    {
        boost::asio::io_service io_service;

        tcp::acceptor acceptor(io_service, tcp::endpoint(tcp::v4(), 13));

        for (;;)
        {
            tcp::socket socket(io_service);
            acceptor.accept(socket);

            std::string message = "This is the Server!";

            boost::system::error_code ignored_error;
            boost::asio::write(socket, boost::asio::buffer(message), ignored_error);
        }
    }
    catch (std::exception& e)
    {
        std::cerr << e.what() << std::endl;
    }

    return 0;
}

error: connect: No connection could be made because the target machine actively refused it. — Anthony Raimondo

DeVadder DeVadder · Accepted Answer · 2013-12-11T07:35:46

I would guess your problem might be that you return on the first error. Resolving gives you an iterator on a number of endpoints. You try the first of those and if it does not work out you give up instead of letting the iterator go on.

Again, i am by no means an expert in boost::asio and far less in its TCP world but resolve may return more than one endpoint (for example IPv4 and IPv6) and possibly only one of them does not work out here. For testing you could create the endpoint yourself by first creating a ip::address object, using its from_string() method to give it the address of the server (works only on your local network of course) and then using it for your endpoint:

boost::asio::ip::address address;
address.from_string("the.servers.ip.here");
boost::asio::ip::tcp::endpoint endpoint(address, 13);
boost::asio::connect(socket, endpoint);

And see if that works. If not, it probably is a problem on the server side.

Boost.asio server-client. Connect between 2 computers

3 Answers