UDP打孔 . 让服务器与客户交谈

4 回答

• 12

  嗯，我觉得你在这里混淆了几件事 . 首先，它真的叫做UDP hole punching . 让我试着解释一下这应该如何运作 .

  NAT路由器在将数据包从内部专用网络转发到外部Internet时通常会执行port mapping .

  假设您在NAT后面的计算机上创建了UDP套接字，并将数据报发送到某个外部IP /端口 . 当携带该数据报的IP数据包离开发送机器时，其IP报头的源地址字段设置为本地不可全局路由的专用IP地址（如 192.168.1.15 ），UDP报头的源端口字段设置为分配的任何端口到套接字（显式地通过绑定，或由OS从临时端口隐式选择） . 我将这个源端口号称为 P1 .

  然后，当NAT路由器在外部网络上发送该数据包时，它会将源IP地址覆盖到其自己的外部IP地址（否则它将 P2 标记为 P2 ）保留在路由器中以匹配返回数据包 . 此映射还可能特定于目标IP地址和目标UDP端口 .

  所以现在你在路由器中有"punched a hole" - 发送回路由器到端口 P2 的UDP数据包被转发到UDP端口 P1 上的内部机器 . 同样，根据NAT实现，这可能仅限于来自原始目标IP地址和目标UDP端口的数据包 .

  对于客户端到客户端的通信，您必须通过服务器将一个外部IP /端口告诉另一个，希望NAT路由器将相同的内部源端口映射到相同的外部源端口 . 然后客户端将使用这些发送数据包 .

  希望这可以帮助 .

  回复于 2024-05-15T03:57:34+08:00
• 0

  终于找到了答案！这是仅使用客户端和服务器的实现 . 我的下一次尝试是使用3台电脑 . 无论如何希望这有助于：

  Server code:

  class Program
  {
      static byte[] dataToSend = new byte[] { 1, 2, 3, 4, 5 };
  
      // get the ip and port number where the client will be listening on
      static IPEndPoint GetClientInfo()
      {
          // wait for client to send data
          using (UdpClient listener = new UdpClient(11000))
          {
              IPEndPoint groupEP = new IPEndPoint(IPAddress.Any, 11000);
              byte[] receive_byte_array = listener.Receive(ref groupEP);
  
              return groupEP;
          }
      }
  
      static void Main(string[] args)
      {
          var info = GetClientInfo(); // get client info
  
          /* NOW THAT WE HAVE THE INFO FROM THE CLIENT WE ARE GONG TO SEND
             DATA TO IT FROM SCRATCH!. NOTE THE CLIENT IS BEHIND A NAT AND
             WE WILL STILL BE ABLE TO SEND PACKAGES TO IT
          */
  
          // create a new client. this client will be created on a 
          // different computer when I do readl udp punch holing
          UdpClient newClient = ConstructUdpClient(info);
  
          // send data
          newClient.Send(dataToSend, dataToSend.Length);            
      }
  
      // Construct a socket with the info received from the client
      static UdpClient ConstructUdpClient(IPEndPoint clientInfo)
      {          
          var ip = clientInfo.Address.ToString();
          var port = clientInfo.Port;
  
          // this is the part I was missing!!!!
          // the local end point must match. this should be the ip this computer is listening on
          // and also the port            
          UdpClient client = new UdpClient(new IPEndPoint( IPAddress.Any, 11000));
  
          // lastly we are missing to set the end points. (ip and port client is listening on)
  
          // the connect method sets the remote endpoints
          client.Connect(ip, port);
  
          return client;
      }
  }
  

  client code:

  string ipOfServer = "192.168.0.139";
  int portServerIsListeningOn = 11000;
  
  // send data to server
  Socket sending_socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
  IPAddress send_to_address = IPAddress.Parse(ipOfServer);
  IPEndPoint sending_end_point = new IPEndPoint(send_to_address, portServerIsListeningOn);
  sending_socket.SendTo(Encoding.ASCII.GetBytes("Test"), sending_end_point);
  
  // get info
  var port = sending_socket.LocalEndPoint.ToString().Split(':')[1];
  
  // now wait for server to send data back
  IPEndPoint groupEP = new IPEndPoint(IPAddress.Any, int.Parse(port));
  byte[] buffer = new byte[1024];
  sending_socket.Receive(buffer); // <----- we can receive data now!!!!!
  

  回复于 2024-05-15T03:57:34+08:00
• 1

  您是否考虑在客户端上使用UPnP配置NAT遍历以允许特定端口上的传入数据包？然后，客户端只需要将入站IP和端口传送到服务器，并等待服务器发送数据包 . http://en.wikipedia.org/wiki/Universal_Plug_and_Play

  回复于 2024-05-15T03:57:34+08:00
• 3

  似乎你可以第一次连接服务器 . 连接成功后，你需要每次关闭和断开连接 . 请检查此示例代码http://codeidol.com/csharp/csharp-network/Connectionless-Sockets/A-Simple-UDP-Application/

  回复于 2024-05-15T03:57:34+08:00