C# TCP客户端发送但不接收消息

Question

我继承了一些 TCP 客户端的代码。它发送一条消息，然后在完成时等待确认消息。目前它发送消息，但是当它等待回复消息时它永远不会收到它。 SendMessage() 方法是外部调用的方法。

我设置了断点，可以看到它命中了 Receive() 方法，但从未命中 ReceiveCallback()

任何朝着正确方向的帮助或推动都将不胜感激。

public class SocketService
{
    private ManualResetEvent connectDone = new ManualResetEvent(false);
    private ManualResetEvent sendDone = new ManualResetEvent(false);
    private ManualResetEvent receiveDone = new ManualResetEvent(false);

    string ipAddress;
    private int portNum;
    string returnMessage;
    // private string hostName = Dns.GetHostName ();

    public SocketService(string ipAddress, int portNum)
    {
        this.ipAddress = ipAddress;
        this.portNum = portNum;
    }

    public event Logging OnLogging;

    private void WriteLogMessage(string message)
    {
        if (this.OnLogging != null)
            this.OnLogging(message);
    }

    //char endOfLineSeparator = (char) 0x1C;
    //char cr = (char) 0x0D;
    //char vt = (char) 0x0B;

    public string SendMessage(string message)
    {
        IPAddress ip = IPAddress.Parse(this.ipAddress);
        IPEndPoint remoteEP = new IPEndPoint(ip, portNum);

        connectDone.Reset();

        Socket client = new Socket(AddressFamily.InterNetwork,
                                    SocketType.Stream,
                                    ProtocolType.Tcp);

        client.BeginConnect(remoteEP,
                            new AsyncCallback(ConnectCallback),
                            client);

        connectDone.WaitOne();

        //sendDone.Reset();

        WriteLogMessage("send message");

        Send(client, message);
        sendDone.WaitOne();

        //receiveDone.Reset();

        WriteLogMessage("receive message");

        Receive(client);
        receiveDone.WaitOne();

        client.Shutdown(SocketShutdown.Both);
        client.Close();

        return this.returnMessage;
    }

    private void Send(Socket client, String data)
    {
        byte[] byteData = Encoding.ASCII.GetBytes(data);

        client.BeginSend(byteData,
                        0,
                        byteData.Length,
                        0,
                        new AsyncCallback(SendCallback),
                        client);
    }

    private void SendCallback(IAsyncResult ar)
    {
        Socket client = (Socket)ar.AsyncState;

        int bytesSent = client.EndSend(ar);

        sendDone.Set();
    }

    private void ConnectCallback(IAsyncResult ar)
    {
        Socket client = (Socket)ar.AsyncState;

        client.EndConnect(ar);

        connectDone.Set();
    }

    private void Receive(Socket client)
    {
        StateObject state = new StateObject(client);

        client.BeginReceive(state.Buffer,
                            0,
                            StateObject.BufferSize,
                            0,
                            new AsyncCallback(ReceiveCallback),
                            state);
    }

    private void ReceiveCallback(IAsyncResult ar)
    {
        StateObject state = (StateObject)ar.AsyncState;
        Socket client = state.WorkSocket;

        int bytesRead = client.EndReceive(ar);

        if (bytesRead > 0)
        {
            state.StoredContent.Append(Encoding.ASCII.GetString(state.Buffer, 0, bytesRead));

            client.BeginReceive(state.Buffer,
                                0,
                                StateObject.BufferSize,
                                0,
                                new AsyncCallback(ReceiveCallback),
                                state);

            WriteLogMessage(state.StoredContent.ToString());
        }
        else
        {
            this.returnMessage = state.StoredContent.ToString();

            receiveDone.Set();
        }
    }
}

Answer 1

您的 SendMessage 和 Receive 函数实际上没有任何作用。他们只是发送和接收字节。他们没有 "message" 的概念，在发送消息时不标记消息的结尾，在接收消息时也不识别消息的结尾。简而言之，您忘记实现网络协议并假设 TCP 是一种消息服务，而实际上它是一种字节流服务。

如果你需要发送和接收消息，你必须精确定义什么是"message"并编写代码来发送和接收它们。它不会变魔术。

Answer 2

正如 David Schwartz 所指出的，您需要一种分隔消息的方法。

看看如何WebSocket data is framed。

0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-------+-+-------------+-------------------------------+
|F|R|R|R| opcode|M| Payload len |    Extended payload length    |
|I|S|S|S|  (4)  |A|     (7)     |             (16/64)           |
|N|V|V|V|       |S|             |   (if payload len==126/127)   |
| |1|2|3|       |K|             |                               |
+-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - +
|     Extended payload length continued, if payload len == 127  |
+ - - - - - - - - - - - - - - - +-------------------------------+
|                               |Masking-key, if MASK set to 1  |
+-------------------------------+-------------------------------+
| Masking-key (continued)       |          Payload Data         |
+-------------------------------- - - - - - - - - - - - - - - - +
:                     Payload Data continued ...                :
+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
|                     Payload Data continued ...                |
+---------------------------------------------------------------+

Answer 3

到头来是无人知晓的事情。这些是 HL7 消息，消息末尾缺少一个隐藏字符。接收方一直在等待消息发送完成，但是没有这个字符就没有看到完整的消息，因此也没有发回确认。

C# TCP客户端发送但不接收消息

C# TCP client sending but not receiving messages

c#

sockets

tcp

websocket