我有一个使用 TCP 连接进行通信的服务器-客户端程序。多个客户端可以同时连接到服务器。我想在这个系统上实现tcp hole punching。

在客户端，它调用公共(public)服务器来查找我的服务器的公共(public) ip、端口。然后连接到它。

但是在服务器端它必须打开一个端口来连接到公共(public)服务器，并且它还必须在同一个端口上接受客户端连接请求。

我要做的是打开一个套接字并绑定(bind)到端口X，然后连接到公共(public)服务器，然后将这个套接字更改为监听状态以接受传入连接一段时间，然后开始连接到公共(public)服务器一次又一次。

这是正确的方法吗？

编辑:我有另一个想法。就是开一个新的端口，连接公用服务器。主服务器端口照常监听传入连接。当客户端要连接时，公共(public)服务器将通过新端口告诉我的服务器。它将阻止主端口监听传入连接，而是连接到客户端进行打洞。然后它连接到公共(public)服务器，它将服务器公共(public) ip 地址转发给客户端，并像往常一样返回监听传入连接。然后客户端将使用此地址连接到已打开 TCP 漏洞的服务器。

最佳答案

最好有两个套接字，并保持服务器和客户端之间的独立连接。

1. m_nServerTCPSocket- 用于与服务器连接和监听套接字

2. m_nPeerPrivateTCPSocket- 连接对端(公共(public)地址)

3. m_nPeerPublicTCPSocket- 与对等点连接(如果其他对等点在同一网络中，则为私有(private)地址)

4. m_nListeningTCPSocket - 用于监听对端的套接字，您需要接受来自对端的连接。

5. m_nConnectedPeerTCPSocket-> 一旦与其他对等方连接，您就会获得此套接字。

   while(end_client)    
   {
   
      FD_ZERO(&fdRead);
      FD_ZERO(&fdWrite);
      FD_ZERO(&fdExcept);    
   
      if (pControlMgr->GetConnectionMgr()->GetListeningTCPSocket()>0)
   
      {
   
           FD_SET (pControlMgr->GetConnectionMgr()->GetListeningTCPSocket(),&fdRead);      
           FD_SET (pControlMgr->GetConnectionMgr()->GetListeningTCPSocket(),&fdExcept);
       }
   
       if (pControlMgr->GetConnectionMgr()->GetServerTCPSocket()>0)
       {
   
           FD_SET (pControlMgr->GetConnectionMgr()->GetServerTCPSocket(),&fdRead); 
           FD_SET (pControlMgr->GetConnectionMgr()->GetServerTCPSocket(),&fdExcept);
   }
       if (pControlMgr->GetConnectionMgr()->GetConnectedTCPSocket()>0)
   {
       FD_SET (pControlMgr->GetConnectionMgr()->GetConnectedTCPSocket(),&fdRead);      
       FD_SET (pControlMgr->GetConnectionMgr()->GetConnectedTCPSocket(),&fdExcept);        
   }
   
   timeval tv;
   tv.tv_sec = 2;
   tv.tv_usec = 0;
   
   nSelectRetVal =  select(NULL,&fdRead,NULL,&fdExcept,&tv);
   
   
   if (nSelectRetVal>0)
   {
       int nRecvRetVal = 0;
       /* TCP Server Socket handling */
       if ( FD_ISSET(pControlMgr->GetConnectionMgr()->GetServerTCPSocket(), &fdRead ))
       {           
           try
           {
               pRecvBuffer =  new char[TCP_RECV_SIZE];
               nRecvRetVal = recv(pControlMgr->GetConnectionMgr()->GetServerTCPSocket(),
                   pRecvBuffer,TCP_RECV_SIZE,
                   0);
               int n = WSAGetLastError();
               if (nRecvRetVal>0)
               {
                   int nPeerNameRetVal = getpeername(pControlMgr->GetConnectionMgr()->GetServerTCPSocket(),(sockaddr*)&addrRemotePeer,&nSockAddrLen);
                   if ( pControlMgr->HandlePacket(pRecvBuffer,addrRemotePeer)== -1 )                       
                   {
                       if ( NULL != pRecvBuffer)
                       {
                           delete [] pRecvBuffer;
                           pRecvBuffer = NULL;
                           return 0 ;
                       }
                   }
               }                           
           }           
           catch (...)
           {
               if ( NULL != pRecvBuffer )
               {
                   delete [] pRecvBuffer;
                   pRecvBuffer = NULL;
               }
           }
   
           if ( NULL != pRecvBuffer)
           {
               delete [] pRecvBuffer;
               pRecvBuffer = NULL;
           }       
       } /* TCP Server Socket handling */      
   
       int n;
       /* TCP Exception Server Socket handling */
       if ( FD_ISSET(pControlMgr->GetConnectionMgr()->GetServerTCPSocket(), &fdExcept ))
       {
           /*FD_CLR(pControlMgr->GetConnectionMgr().GetServerTCPSocket (),&fdRead);
           FD_CLR(pControlMgr->GetConnectionMgr().GetServerTCPSocket (),&fdExcept);*/
           n = WSAGetLastError();
           //return 0;
       }   
          if (FD_ISSET(pControlMgr->GetConnectionMgr()->GetListeningTCPSocket(),&fdRead))
       {
           sockaddr_in addrConnectedPeer;
           int nAddrLen =sizeof(addrConnectedPeer) ;
           int nConnectedSock = accept( pControlMgr->GetConnectionMgr()->GetListeningTCPSocket(),
               (sockaddr*)&addrConnectedPeer,
               &nAddrLen);
           int n1 = WSAGetLastError();
           if (nConnectedSock>0)
           {
               pControlMgr->GetConnectionMgr()->SetConnectedTCPSocket(nConnectedSock);
               int n = pControlMgr->GetConnectionMgr()->GetConnectedTCPSocket();
               continue;
           }
       }
       /* TCP Exception Listening Socket handling */
       if ( FD_ISSET(pControlMgr->GetConnectionMgr()->GetListeningTCPSocket(), &fdExcept ))
       {
           FD_CLR(pControlMgr->GetConnectionMgr()->GetListeningTCPSocket (),&fdRead);
           FD_CLR(pControlMgr->GetConnectionMgr()->GetListeningTCPSocket (),&fdExcept);
           //return 0;
       }   /* TCP Exception Listening Socket handling */   
   
       /* Connected Peer TCP Read Socket handling */
       if ( FD_ISSET(pControlMgr->GetConnectionMgr()->GetConnectedTCPSocket(), &fdRead ))
       {           
           try
           {
               pRecvBuffer =  new char[TCP_RECV_SIZE];
               nRecvRetVal = recv (pControlMgr->GetConnectionMgr()->GetConnectedTCPSocket(),
                   pRecvBuffer,TCP_RECV_SIZE,
                   0);
               if (nRecvRetVal>0)
               {
                   int nPeerNameRetVal = getpeername(pControlMgr->GetConnectionMgr()->GetConnectedTCPSocket(),(sockaddr*)&addrRemotePeer,&nSockAddrLen);
                   if ( pControlMgr->HandlePacket(pRecvBuffer,addrRemotePeer)== -1 )                       
                   {
                       if ( NULL != pRecvBuffer)
                       {
                           delete [] pRecvBuffer;
                           pRecvBuffer = NULL;
                           return 0 ;
                       }
                   }
               }                           
           }           
           catch (...)
           {
               if ( NULL != pRecvBuffer )
               {
                   delete [] pRecvBuffer;
                   pRecvBuffer = NULL;
               }
           }
           //FD_CLR(pControlMgr->GetConnectionMgr().GetConnectedTCPSocket(),&fdRead);  
           if ( NULL != pRecvBuffer)
           {
               delete [] pRecvBuffer;
               pRecvBuffer = NULL;
           }       
       } /* Peer TCP Read Socket handling */   
       /* TCP Exception Connected Socket handling */
       if ( FD_ISSET(pControlMgr->GetConnectionMgr()->GetConnectedTCPSocket(), &fdExcept ))
       {
           /*FD_CLR(pControlMgr->GetConnectionMgr()->GetConnectedTCPSocket (),&fdRead);
           FD_CLR(pControlMgr->GetConnectionMgr()->GetConnectedTCPSocket (),&fdExcept);
           return 0;*/
           n = WSAGetLastError();
       }
   

创建套接字的逻辑

      int CConnectionMgr::CreateSocket(const int nSockType)
      {
       //TODO: Add code here    
           if (InitWinSock() == -1) 
       {
        return -1;      
       }
       SetLocalIPAddress(); 

       m_nListeningTCPSocket = socket(AF_INET, SOCK_STREAM ,nSockType );                    
       if ( GetListeningTCPSocket() <0 )
        return -1;  
       if (BindSocket(GetListeningTCPSocket())<0)
        return -1;
       int nListenRet = listen(GetListeningTCPSocket(),SOMAXCONN);

        if (nListenRet!=0)
        {
        return -1;
         }      
         m_nPeerPrivateTCPSocket = socket(AF_INET, SOCK_STREAM ,nSockType );
         if (GetPeerPrivateTCPSocket()<0)
         return -1; 
        if (BindSocket(GetPeerPrivateTCPSocket())<0)
         return -1;

         m_nPeerPublicTCPSocket = socket(AF_INET, SOCK_STREAM ,nSockType );
         if ( GetPeerPublicTCPSocket()<0)
           return -1;
          if (BindSocket(GetPeerPublicTCPSocket())<0)
           return -1;

          m_nServerTCPSocket = socket(AF_INET, SOCK_STREAM ,nSockType );
          if (GetServerTCPSocket()<0)
           return -1;
          if (BindSocket(GetServerTCPSocket())<0)
           return -1;
        return 1;
         }

关于networking - 如何控制peer上的socket[TCP Hole Punching]，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/13118144/