C# TCP 客户端读取偶尔不会收到任何数据 - “无”

本文关键字：数据 任何 客户端 TCP 读取 偶尔 | 更新日期: 2023-09-27 18:31:51

我写了一个与服务器通信的TCP客户端。在专用的"侦听"线程中，我有如下代码。它应该只在有一些数据时才读取数据。（ if (stream.DataAvailable) ）

奇怪的是，偶尔我的程序会崩溃，因为流绝对不会读取任何数据。它将返回一个空string。更奇怪的是，如果我尝试在handleResponse(string s)函数中"捕获"一个空字符串，它不会被捕获。

    public void listenForResponses()
    {
        Console.WriteLine ("Listening...");
        while (isConnected == true)
        {
            Thread.Sleep (updateRate);
            String responseData = String.Empty;
            if (stream.DataAvailable) {
                Int32 bytes = stream.Read (data, 0, data.Length);
                Console.WriteLine (" >> Data size = "+data.Length);
                responseData = System.Text.Encoding.ASCII.GetString (data, 0, bytes);
                output = responseData+"";
                handleResponse (output);
            }
            if (isConnected == false) {
                closeConnection ();
            }
        }
    }
public void handleResponse(string msg)
{
    Console.WriteLine ("Received: "+msg); 
    iterateThroughEachCharInString (msg);
    if ((msg != "")&&(msg != null)&&(msg != " ")) {
        JSONDataObject desrlzdResp = JsonConvert.DeserializeObject<JSONDataObject>(msg);
        if ((desrlzdResp.instruction != null)) {
            if (desrlzdResp.instruction == "TestConn") {
                handleTestConn (desrlzdResp);
            } else if (desrlzdResp.instruction == "SceneOver") {
                handleSceneFinished (desrlzdResp);
            }
        }
    }
}

引发的异常System.NullReferenceException在 handleResponse 函数的行if ((desrlzdResp.instruction != null))上

C# TCP 客户端读取偶尔不会收到任何数据 - “无”

网络流习惯于播发数据，即使它们不活跃。此外，除非发送方事先通告，否则接收方无法知道传入流有多长。

        /// <summary>
        /// Method designed to allow the sending of Byte[] data to the Peer
        /// Because this is using NetworkStreams - the first 4 bytes sent is the data length
        /// </summary>
        /// <param name="TheMessage"></param>
        public void SendBytesToPeer(byte[] TheMessage)
        {
            try
            {
                long len = TheMessage.Length;
                byte[] Bytelen = BitConverter.GetBytes(len);
                PeerStream.Write(Bytelen, 0, Bytelen.Length);
                PeerStream.Flush();
                PeerStream.Write(TheMessage, 0, TheMessage.Length);
                PeerStream.Flush();
            }
            catch (Exception e)
            {
                //System.Windows.Forms.MessageBox.Show(e.ToString());
            }
        }

注意 - 发送方的刷新可能不需要，但我添加它，因为它没有害处 - Microsoft说刷新对网络流没有任何作用。

因此，此代码将确定您发送的消息的大小，然后在"实际"消息之前将其发送给接收方。

        /// <summary>
        /// Incoming bytes are retrieved in this method
        /// </summary>
        /// <param name="disconnected"></param>
        /// <returns></returns>
        private byte[] ReceivedBytes(ref bool disconnected)
        {
            try
            {
                //byte[] myReadBuffer = new byte[1024];
                int receivedDataLength = 0;
                byte[] data = { };
                int len = 0;
                int i = 0;
                PeerStream.ReadTimeout = 15000;

                if (PeerStream.CanRead)
                {
                    //networkStream.Read(byteLen, 0, 8)
                    byte[] byteLen = new byte[8];
                    if (_client.Client.IsConnected() == false)
                    {
                        //Fire Disconnect event
                        if (OnDisconnect != null)
                        {
                            disconnected = true;
                            OnDisconnect(this);
                            return null;
                        }
                    }
                    while (len == 0)
                    {
                        PeerStream.Read(byteLen, 0, 8);
                        len = BitConverter.ToInt32(byteLen, 0);
                    }
                    data = new byte[len];
                    PeerStream.Read(data, receivedDataLength, len);
                    return data;
                }

            }
            catch (Exception E)
            {
                //System.Windows.Forms.MessageBox.Show("Exception:" + E.ToString());
            }
            return null;
        }

此代码将等到接收器检测到传入的流长度，然后它将尝试读取该确切长度。不要担心OnT断开连接位 - 这只是我从我正在做的项目中留下的一些代码。您可能需要考虑在while（len == 0）循环中添加一个Thread.Sleep，以节省CPU周期。

相关文章：