Socket over internet in C++

Question

I want to understand more about sending data over internet. I have been searching A LOT everywhere but nothing helped... I'm using MinGw and please dont say that i have to change my developer program. So far i made this from what I found: And it work great but only for my local network. Can anyone tell me how i can do the same thing only over the internet?

using namespace std;
#pragma once
#include <iostream>
#include "WinSock2.h"
const int STRLEN = 256;

class Socket
{
    protected:
        WSADATA wsaData;
        SOCKET mySocket;
        SOCKET myBackup;
        SOCKET acceptSocket;
        sockaddr_in myAddress;
    public:
        Socket();
        ~Socket();
        bool SendData( char* );
        bool RecvData( char*, int );
        void CloseConnection();
        void GetAndSendMessage();
};

class ServerSocket : public Socket
{
    public:
        void Listen();
        void Bind( int port );
        void StartHosting( int port );
};

class ClientSocket : public Socket
{
    public:
        void ConnectToServer( const char *ipAddress, int port );
};


Socket::Socket()
{
    if( WSAStartup( MAKEWORD(2, 2), &wsaData ) != NO_ERROR )
    {
        cerr<<"Socket Initialization: Error with WSAStartup\n";
        system("pause");
        WSACleanup();
        exit(10);
    }

    //Create a socket
    mySocket = socket( AF_INET, SOCK_STREAM, IPPROTO_TCP );

    if ( mySocket == INVALID_SOCKET )
    {
        cerr<<"Socket Initialization: Error creating socket"<<endl;
        system("pause");
        WSACleanup();
        exit(11);
    }

    myBackup = mySocket;
}

Socket::~Socket()
{
    WSACleanup();
}

bool Socket::SendData( char *buffer )
{
    send( mySocket, buffer, strlen( buffer ), 0 );
    return true;
}

bool Socket::RecvData( char *buffer, int size )
{
    int i = recv( mySocket, buffer, size, 0 );
    buffer[i] = '\0';
    return true;
}

void Socket::CloseConnection()
{
    //cout<<"CLOSE CONNECTION"<<endl;
    closesocket( mySocket );
    mySocket = myBackup;
}

void Socket::GetAndSendMessage()
{
    char message[STRLEN];
    cin.ignore();//without this, it gets the return char from the last cin and ignores the following one!
    cout<<"Send > ";
    cin.get( message, STRLEN );
    SendData( message );
}

void ServerSocket::StartHosting( int port )
{
     Bind( port );
     Listen();
}

void ServerSocket::Listen()
{
    //cout<<"LISTEN FOR CLIENT..."<<endl;

    if ( listen ( mySocket, 1 ) == SOCKET_ERROR )
    {
        cerr<<"ServerSocket: Error listening on socket\n";
        system("pause");
        WSACleanup();
        exit(15);
    }

    //cout<<"ACCEPT CONNECTION..."<<endl;

    acceptSocket = accept( myBackup, NULL, NULL );
    while ( acceptSocket == SOCKET_ERROR )
    {
        acceptSocket = accept( myBackup, NULL, NULL );
    }
    mySocket = acceptSocket;
}

void ServerSocket::Bind( int port )
{
    myAddress.sin_family = AF_INET;
    myAddress.sin_addr.s_addr = inet_addr( "0.0.0.0" );
    myAddress.sin_port = htons( port );

    //cout<<"BIND TO PORT "<<port<<endl;

    if ( bind ( mySocket, (SOCKADDR*) &myAddress, sizeof( myAddress) ) == SOCKET_ERROR )
    {
        cerr<<"ServerSocket: Failed to connect\n";
        system("pause");
        WSACleanup();
        exit(14);
    }
}

void ClientSocket::ConnectToServer( const char *ipAddress, int port )
{
    myAddress.sin_family = AF_INET;
    myAddress.sin_addr.s_addr = inet_addr( ipAddress );
    myAddress.sin_port = htons( port );

    //cout<<"CONNECTED"<<endl;

    if ( connect( mySocket, (SOCKADDR*) &myAddress, sizeof( myAddress ) ) == SOCKET_ERROR )
    {
        cerr<<"ClientSocket: Failed to connect\n";
        system("pause");
        WSACleanup();
        exit(13);
    } 
}

int main()
{
    int choice;
    int port = 666;
    //char *ipAddress = "127.0.0.1";
    string ipAddress;
    bool done = false;
    char recMessage[STRLEN];
    char sendMessage[STRLEN];
    cout<<"1) Host server"<<endl;
    cout<<"2) Join server"<<endl;
    cout<<"3) Quit"<<endl;
    cin>>choice;
    if ( choice == 3 )
        exit(0);
    else if ( choice == 2 )
    {
        //Client
        cout<<"Enter an IP address, 127.0.0.1 is the loopback address"<<endl;
        cin>>ipAddress;
        ClientSocket sockClient;
        cout<<"ATTEMPTING TO CONNECT..."<<endl;
        sockClient.ConnectToServer( ipAddress.c_str(), port );
        //Connected
        while ( !done )
        {     
            sockClient.GetAndSendMessage();
            cout<<"\t--WAIT--"<<endl;
            sockClient.RecvData( recMessage, STRLEN );
            cout<<"Recv > "<<recMessage<<endl;
            if ( strcmp( recMessage, "end" ) == 0 ||
                        strcmp( sendMessage, "end" ) == 0 )
            {
                done = true;
            }
        }
        sockClient.CloseConnection();
    }
    else if ( choice == 1 )
    {
        //SERVER
        ServerSocket sockServer;
        cout<<"HOSTING..."<<endl;
        sockServer.StartHosting( port );
        //sockServer.StartHosting( port );
        //Connected
        while ( !done )
        {
            cout<<"\t--WAIT--"<<endl;
            sockServer.RecvData( recMessage, STRLEN );
            cout<<"Recv > "<<recMessage<<endl;
            sockServer.GetAndSendMessage();
            if ( strcmp( recMessage, "end" ) == 0 || strcmp( sendMessage, "end" ) == 0 )
            {
                done = true;
            }
        }
    }
}

Thanks to all who responded but, you gave me a lot to read when i just asked what part of the code should be changed so i can use the internet. Obviously I cant understand half of what is written there. Still nothing helped.

Answer 1

If you want to use sockets over the internet and you want your application to be usable on every network setting, including NAT, you will have to use a TCP Holepunch called technique (or UDP holepunching may also fit). I think your approach is not working because there is some NAT between your endpoints, so socket connections fail.

I suggest to investigate on NAT. Peer-to-Peer Communication Across Network Address Translators

And this discussion here on SO

Answer 2

What is it that you don't understand? I see the code and it's binding to a local socket and then you connect to it with a client. You can do this over the internet as well but what is it that you aren't understanding about the process? I'm afraid you may need to start learning the basics of TCP/IP before trying to write socket code. It's like trying to start out learning engineering by building a space shuttle.

Answer 3

The ability to host a service that's visible from the Internet is very dependent on the type of the Internet connection you've got. If you're behind a NAT, you'll need to set up a NAT port forwarding. If your IP address is dynamic, you'll need to know your publicly available IP address (try http://www.whatismyip.com/).