c++ - C++中的互联网套接字

Question

我想了解有关通过 Internet 发送数据的更多信息。 我一直在到处搜索，但没有任何帮助...... 我正在使用 MinGw，请不要说我必须更改我的开发人员程序。 到目前为止，我是根据我发现的内容制作的: 它工作得很好，但只适用于我的本地网络。谁能告诉我如何仅通过互联网做同样的事情？

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;
            }
        }
    }
}

感谢所有回复的人，但是，当我刚刚询问应该更改代码的哪一部分以便我可以使用互联网时，你们给了我很多阅读的机会。显然我不能理解那里写的一半内容。仍然没有任何帮助。

Answer 1

如果你想在互联网上使用套接字，并且你希望你的应用程序在每个网络设置上都可用，包括 NAT，你将不得不使用称为技术的 TCP 打洞(或者 UDP 打洞也可能适合)。我认为你的方法不起作用 因为在您的端点之间存在一些 NAT，所以套接字连接失败。

我建议调查 NAT。 Peer-to-Peer Communication Across Network Address Translators

和this discussion here on SO