Question

在我的服务器应用程序的网络协议中，我发送的每个缓冲区的开头都有2个字节，包含长度。并且TcpReadCallback方法读取BeginReceive写入的字节，直到读取完整的缓冲区。然而，使用我的实现，数据包似乎丢失，有时空缓冲区被发送到ProcessReceiveBuffer，尤其是当我发送5ms以下的消息时，以及通过互联网发送时更常见（将发生在10或所以秒发送半秒钟）。有谁能在这里发现我做错了什么？

谢谢！

[17:29:49]: received: 1349, 514
[17:29:50]: received: 1350, 514
[17:29:50]: received: 1351, 514
[17:29:51]: received: 1352, 514
[17:29:51]: received: 1353, 514
[17:29:52]: received: 1355, 514
[17:29:52]: Skipped! expected 1354, got 1355
[17:29:53]: received: 1357, 514
[17:29:53]: Skipped! expected 1356, got 1357
[17:29:54]: received: 1359, 514
[17:29:54]: Skipped! expected 1358, got 1359
[17:29:56]: received: 1362, 514
[17:29:56]: Skipped! expected 1360, got 1362
[17:29:56]: received: 1363, 514
[17:29:57]: received: 1364, 514

示例：

＆＃34;收到＆＃34;之后的第一个号码是客户发送的订单，其次是尺寸。当通过互联网发送时，一些数据包经常以突发方式丢弃在TCP中。

print(Unmanaged.passUnretained(someVar).toOpaque())

Answer 1

由于网络拥塞，EndReceive可能无法一次性收到完整的消息。因此TcpReadCallback应重复读取操作，直到不再接收到字节为止。

以下是相关的MSDN example，其中说明了这一点：

public static void Read_Callback(IAsyncResult ar){
    StateObject so = (StateObject) ar.AsyncState;
    Socket s = so.workSocket;

    int read = s.EndReceive(ar);

    if (read > 0) {
            so.sb.Append(Encoding.ASCII.GetString(so.buffer, 0, read));
            s.BeginReceive(so.buffer, 0, StateObject.BUFFER_SIZE, 0, 
                                     new AsyncCallback(Async_Send_Receive.Read_Callback), so);
    }
    else{
         if (so.sb.Length > 1) {
              //All of the data has been read, so displays it to the console
              string strContent;
              strContent = so.sb.ToString();
              Console.WriteLine(String.Format("Read {0} byte from socket" + 
                               "data = {1} ", strContent.Length, strContent));
         }
         s.Close();
    }
}

在related post中讨论了对操作系统级别的基本tcp socket send()和recv()调用中的类似效果。

Answer 2

我已使用https://github.com/Luaancz/Networking

中的实现解决了这个问题

一些数据包在异步tcp Socket中丢失

2 个答案: