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;
}

Answer 1

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.

Answer 2

To run the server and client on separate networks, Make the client connect to the servers external ip address. This is obvious but external ip addresses constantly change so to solve this problem you can go to www.noip.com and create a name that links to your ip address. This way in the client all you have to do is specify a name instead of an ip address.

Answer 3

最可能的防火墙问题，如果您使用Windows服务器进行检查Windows防火墙，如果使用Linux服务器，请检查iptables。