在 C# 中接收和发送数据

Question

我仍在努力改进我之前写的内容。 现在我遇到了接收数据的问题。我有一个程序，我用它使用 tcpClient 将字符串发送到我正在侦听指定端口的程序。它工作正常，所以我决定再发送一次数据

public static void receiveThread()
{
    while (true)
    {
        TcpListener tcpListener = new TcpListener(IPAddress.Any, port);
        tcpListener.Start();

        Console.WriteLine("Waiting for connection...");

        TcpClient tcpClient = tcpListener.AcceptTcpClient();

        Console.WriteLine("Connected with {0}", tcpClient.Client.RemoteEndPoint);

        while (!(tcpClient.Client.Poll(20, SelectMode.SelectRead)))
        {
            NetworkStream networkStream = tcpClient.GetStream();
            StreamReader streamReader = new StreamReader(networkStream);

            data = streamReader.ReadLine();

            if (data != null)
            {
                Console.WriteLine("Received data: {0}", data);
                send(data); // Here Im using send Method
            }
        }
        Console.WriteLine("Dissconnected...\n");
        tcpListener.Stop();
    }
}

/// <summary>
/// Sending data
/// </summary>
/// <param name="data">Data to send</param>
public static void send(string data)
{
    TcpClient tcpClient = new TcpClient();
    try
    {
        tcpClient.Connect(ipAddress, sendPort);
        Console.WriteLine("Connected with {0}", tcpClient.Client.RemoteEndPoint);
    }
    catch (Exception e)
    {
        Console.WriteLine(e);
    }
    if (tcpClient.Connected)
    {
        NetworkStream networkStream = tcpClient.GetStream();
        StreamWriter streamWriter = new StreamWriter(networkStream);
        Console.WriteLine("Messege {0} to {1}", data, tcpClient.Client.RemoteEndPoint);
        streamWriter.WriteLine(data);
        streamWriter.Flush();
        tcpClient.Close();
    }
}

有时它可以正常工作，但更多时候，我们称它为接收器，但无法获取我试图发送的内容。我真的不知道它有什么问题。看起来发送方法可能有问题。这是接收器输出的示例

Waiting for connection...
Connected with 127.0.0.1:52449
Dissconnected...

Waiting for connection...
Connected with 127.0.0.1:52450
Received data: qweqwe
Dissconnected...

Waiting for connection...
Connected with 127.0.0.1:52451
Dissconnected...

Waiting for connection...
Connected with 127.0.0.1:52452
Dissconnected...

Waiting for connection...
Connected with 127.0.0.1:52453
Received data: zxczx
Dissconnected...

Waiting for connection...
Connected with 127.0.0.1:52454
Dissconnected...

Waiting for connection...
Connected with 127.0.0.1:52455
Received data: aasd
Dissconnected...

Waiting for connection...
Connected with 127.0.0.1:52457
Received data: www
Dissconnected...

Answer 1

这里有几个问题：

1. StreamReader 有一个 4kB 的缓冲区，并会在第一次调用 ReadLine() 时尝试尽可能多地读取。结果是您可能在 StreamReader 中有数据，并在没有更多可用数据时进入 Poll()，因为它已被读取。
2. Poll() 需要几微秒。等待传入数据 0.02ms 可能会返回 false，除非在您调用 Poll() 之前数据已经存在。
3. 您在每次迭代时都创建一个新的 StreamReader，这可能会丢弃前一个迭代中已读取的数据。

如果您只是要阅读行并想要超时和StreamReader，我会这样做：

delegate string ReadLineDelegate ();
...
using (NetworkStream networkStream = tcpClient.GetStream()) {
    StreamReader reader = new StreamReader(networkStream);
    ReadLineDelegate rl = new ReadLineDelegate (reader.ReadLine);
    while (true) {
        IAsyncResult ares = rl.BeginInvoke (null, null);
        if (ares.AsyncWaitHandle.WaitOne (100) == false)
            break; // stop after waiting 100ms
        string str = rl.EndInvoke (ares);
        if (str != null) {
            Console.WriteLine ("Received: {0}", str);
            send (str);
        } 
    }
}

Answer 2

在追鬼之前确保数据确实存在于流中。如果总是有数据，我们可以解决问题，但是从逻辑上看，它看起来好像流要么被清空，要么上面没有数据。