如何设置TCPListener始终监听，并在新连接时丢弃当前连接。

Question

我想承认我在C#方面并不是最强的，我通过查看几个教程来开发这个程序，如果您能详细回答我的问题，我将不胜感激。
我希望我的TCP服务器始终监听传入的连接，当一个新的TCP客户端连接时，我希望它放弃旧连接并使用新连接。

我尝试实现这个答案：https://dev59.com/sWIk5IYBdhLWcg3wUsrv#19387431
但我的问题是，当我模拟TCP客户端时，上面的答案只会接收一条消息（而我的当前代码会接收所有发送的消息），我也尝试转换数据，以便以与下面的代码相同的方式接收它，但没有成功。
此外，我认为上面的代码仅接受新客户端，而不会丢弃先前连接的客户端。

我的当前代码可以处理连接，并在断开连接后搜索新连接，我希望始终寻找新连接，如果新客户端要连接，则放弃当前连接，让新客户端通过

public class TCPListener
{
    public static void Listener()
    {
        TcpListener server = null;
        try
        {
            // Set the TcpListener on carPort.
            Int32 port = 5002;

            // TcpListener server = new TcpListener(port);
            server = new TcpListener(IPAddress.Any, port);

            // Start listening for client requests.
            server.Start();

            // Buffer for reading data
            Byte[] bytes = new Byte[256];
            String data = null;

            // Enter the listening loop.
            while (true)
            {
                Console.Write("Waiting for a connection... ");

                // Perform a blocking call to accept requests.
                TcpClient client = server.AcceptTcpClient();
                Console.WriteLine("Connected!");

                // Get a stream object for reading
                NetworkStream stream = client.GetStream();

                int i;

                // Loop to receive all the data sent by the client.
                while ((i = stream.Read(bytes, 0, bytes.Length)) != 0)
                {
                    // Translate data bytes to a ASCII string.
                    data = System.Text.Encoding.ASCII.GetString(bytes, 0, i);
                    Console.WriteLine("Received: {0}", data);
                }
                // Shutdown and end connection
                Console.WriteLine("Client close");
                client.Close();
            }
        }
        catch (SocketException e)
        {
            Console.WriteLine("SocketException: {0}", e);
        }
        finally
        {
            // Stop listening for new clients.
            Console.WriteLine("Stop listening for new clients.");
            server.Stop();
        }

    }
}

编辑：如果有人需要解决我的问题，那么这就是我应用了Cecilio Pardo建议的代码，非常有效！

public class TCPListener
{
    Form form = new Form();
    public static void Listener()
    {
        TcpListener server = null;
        try
        {
            // Set the TcpListener on carPort.
            Int32 port = 5002;

            // TcpListener server = new TcpListener(port);
            server = new TcpListener(IPAddress.Any, port);

            // Start listening for client requests.
            server.Start();

            // Buffer for reading data
            Byte[] bytes = new Byte[256];
            String data = null;

            // Enter the listening loop.
            while (true)
            {
                Console.Write("Waiting for a connection... ");

                // Perform a blocking call to accept requests.
                TcpClient client = server.AcceptTcpClient();
                Console.WriteLine("Connected!");

                data = null;
                bool dataAvailable = false;
                // Get a stream object for reading
                NetworkStream stream = client.GetStream();

                int i;
                while (true)
                {
                    if (!dataAvailable)
                    {
                        dataAvailable = stream.DataAvailable;
                        //Console.WriteLine("Data Available: "+dataAvailable);
                        if (server.Pending())
                        {
                            Console.WriteLine("found new client");
                            break;
                        }
                    }

                    if (dataAvailable)
                    {
                        // Loop to receive all the data sent by the client.
                        i = stream.Read(bytes, 0, bytes.Length);
                        data = System.Text.Encoding.ASCII.GetString(bytes, 0, i);

                        Console.WriteLine("Received: {0}", data);
                        dataAvailable = false;
                    }

                    if (server.Pending())
                    {
                        Console.WriteLine("found new client");
                        break;
                    }
                }

                Console.WriteLine("Client close");
                // Shutdown and end connection
                client.Close();
            }
        }
        catch (SocketException e)
        {
            Console.WriteLine("SocketException: {0}", e);
        }
        finally
        {
            // Stop listening for new clients.
            Console.WriteLine("Stop listening for new clients.");
            server.Stop();
        }

    }
}

- MikeyR

Answer 1

当你处于内部的 while 循环中时，无法检查新连接。因此，你需要在循环内添加类似以下内容的代码：

if ( server.Pending() ) break;

那将在等待另一个连接时退出循环。

另一个问题是，stream.Read会阻塞直到有数据可用，因此如果活动连接处于空闲状态，则不会处理新连接。因此，您需要进行更改，并且仅在有数据时调用Read，使用stream.DataAvailable。

- Cecilio Pardo

---

经过一番努力，我终于通过你的解决方案使所有东西都能正常工作了！非常感谢你！ - MikeyR

Answer 2

这是我正在使用的代码，目前效果还不错，我刚开始开发这种类型的应用程序。如果我对这段代码进行了重大更改或发现了错误，我会进行更新：

class ClientListener
{
    const int PORT_NO = 4500;
    const string SERVER_IP = "127.0.0.1";
    private TcpListener listener;

    public async Task Listen()
    {
        IPAddress localAddress = IPAddress.Parse(SERVER_IP);
        listener = new TcpListener(localAddress, PORT_NO);
        Console.WriteLine("Listening on: " + SERVER_IP + ":" + PORT_NO);
        listener.Start();

        while (true)
        {
            // Accept incoming connection that matches IP / Port number
            // We need some form of security here later
            TcpClient client = await listener.AcceptTcpClientAsync();

            if (client.Connected)
            {
                // Get the stream of data send by the server and create a buffer of data we can read
                NetworkStream stream = client.GetStream();
                byte[] buffer = new byte[client.ReceiveBufferSize];

                int bytesRead = stream.Read(buffer, 0, client.ReceiveBufferSize);

                // Convert the data recieved into a string
                string data = Encoding.ASCII.GetString(buffer, 0, bytesRead);
                Console.WriteLine("Recieved Data: " + data);
            }
        }
    }

    public void StopListening()
    {
        listener.Stop();
    }
}

- jeninja