C#接收和发送数据 [英] Receiving and sending data in C#

问题描述

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，用于使用 tcpClient 将字符串发送到我在指定端口上侦听的程序.它工作正常，所以我决定再发送一次数据

I'm still trying to improve a little bit what I wrote before. Now I faced a problem with receiving data. I have a program which I use to send string using tcpClient to a program in which Im listening on a specified port. It works fine so I decided to send data forward one more time

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();
    }
}

有时它工作正常，但更多时候，我们称其为接收器，无法得到我想要发送的内容.我真的不知道它有什么问题.看起来 send 方法可能有问题.这是接收器输出的示例

Sometimes it works fine, but more often, lets call it a receiver, can't get what Im trying to send. And I really do not konw what is wrong with it. Looks like there can be a problem with send method. Here is an example of receivers output

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...

推荐答案

这里有几个问题:

1. StreamReader 有一个 4kB 的缓冲区，并且会在第一次调用 ReadLine() 时尝试读取尽可能多的内容.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 0.02 毫秒 以获取传入数据可能会返回 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，这可能会丢弃前一次已读取的数据.

1. StreamReader has a 4kB buffer and will try to read as much as possible in the first call to ReadLine(). The result is that you might have data in the StreamReader and go into Poll() when there's no more data available because it's already been read.
2. Poll() takes microseconds. Waiting 0.02ms for incoming data is likely to return false unless the data is there before you call Poll().
3. You create a new StreamReader on every iteration, which might discard data already read in the previous one.

如果您只是要阅读行并想要超时和StreamReader，我会这样做:

If you're just going to read lines and want a timeout and a StreamReader, I would do something like:

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);
        } 
    }
}

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