如何在控制台应用程序中保持客户端套接字连接打开并 send/receive 多条消息

Question

我正在通过 TCP 套接字连接到服务器并发送数据字符串并期待响应。响应对于请求字符串是唯一的，每个请求有两个响应。一个表示服务器完成了中间任务，另一个表示任务已完成。这些任务最多需要大约 20 秒才能完成。注意 - 我无权访问服务器 program/code 其专有。

客户端应该能够随时发送字符串请求，有时还相当快。请求可能会堆积起来，客户端需要等待收到每个请求的唯一响应。

假设这需要一个异步客户端，我正在使用来自 MS 站点的示例。

https://docs.microsoft.com/en-us/dotnet/framework/network-programming/asynchronous-client-socket-example

在控制台应用程序中开发，我能够连接并发送字符串请求，并得到一个响应。然后程序退出。异步套接字的新手我不确定如何保持套接字“活动”或打开并随机 Console.Read 新字符串，发送它们，并在收到它们时获得两个响应。

这是我的客户端代码。

public static Socket ClientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

// State object for receiving data from remote device.  
public class StateObject
{
    // Client socket.  
    public Socket workSocket = null;
    // Size of receive buffer.  
    public const int BufferSize = 256;
    // Receive buffer.  
    public byte[] buffer = new byte[BufferSize];
    // Received data string.  
    public StringBuilder sb = new StringBuilder();
}

public class AsynchronousClient
{

    // ManualResetEvent instances signal completion.  
    private static ManualResetEvent connectDone =
        new ManualResetEvent(false);
    private static ManualResetEvent sendDone =
        new ManualResetEvent(false);
    private static ManualResetEvent receiveDone =
        new ManualResetEvent(false);

    // The response from the remote device.  
    private static String response = String.Empty;

    public static void StartClient()
    {
        // Connect to a remote device.  
        try
        {
            IPEndPoint remoteEP = new IPEndPoint(ip, port);

            // Create a TCP/IP socket.  
            Socket client = new Socket(ip.AddressFamily,
                SocketType.Stream, ProtocolType.Tcp);

            // Connect to the remote endpoint.  
            client.BeginConnect(remoteEP,
                new AsyncCallback(ConnectCallback), client);
            connectDone.WaitOne();

            Console.WriteLine("Enter a message string: \n");

            message = Console.ReadLine();

            // Send test data to the remote device.  
            Send(client, message + "\r\n");  // \r\n required for server to know end of string
            sendDone.WaitOne();

            // Receive the response from the remote device.  
            Receive(client);
            receiveDone.WaitOne();

            // Write the response to the console.  
            Console.WriteLine("Response received : {0}", response);

        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

    private static void ConnectCallback(IAsyncResult ar)
    {
        try
        {
            // Retrieve the socket from the state object.  
            Socket client = (Socket)ar.AsyncState;

            // Complete the connection.  
            client.EndConnect(ar);

            Console.WriteLine("Connected to:  {0}", client.RemoteEndPoint.ToString());

            // Signal that the connection has been made.  
            connectDone.Set();
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

    private static void Receive(Socket client)
    {
        try
        {
            // Create the state object.  
            StateObject state = new StateObject();
            state.workSocket = client;

            // Begin receiving the data from the remote device.  
            client.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, 
                new AsyncCallback(ReceiveCallback), state);

        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

    private static void ReceiveCallback(IAsyncResult ar)
    {
        try
        {
            // Retrieve the state object and the client socket
            // from the asynchronous state object.  
            StateObject state = (StateObject)ar.AsyncState;
            Socket client = state.workSocket;

            // Read data from the remote device.  
            int bytesRead = client.EndReceive(ar);

            if (bytesRead > 0)
            {
                // There might be more data, so store the data received so far.  
                state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, bytesRead));

                // Get the rest of the data.  
                client.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                    new AsyncCallback(ReceiveCallback), state);
            }
            else
            {
                // All the data has arrived; put it in response.  
                if (state.sb.Length > 1)
                {
                    response = state.sb.ToString();
                }
                // Signal that all bytes have been received.  
                receiveDone.Set();
            }

            // Added this here to see if receiving would continue, does not work
            client.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, 
                new AsyncCallback(ReceiveCallback), state);

        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

    private static void Send(Socket client, String data)
    {
        // Convert the string data to byte data using ASCII encoding.  
        byte[] byteData = Encoding.ASCII.GetBytes(data);

        // Begin sending the data to the remote device.  
        client.BeginSend(byteData, 0, byteData.Length, 0, new AsyncCallback(SendCallback), client);

    }

    private static void SendCallback(IAsyncResult ar)
    {
        try
        {
            // Retrieve the socket from the state object.  
            Socket client = (Socket)ar.AsyncState;

            // Complete sending the data to the remote device.  
            int bytesSent = client.EndSend(ar);
            Console.WriteLine("Sent {0} bytes to server.", bytesSent);

            // Signal that all bytes have been sent.  
            sendDone.Set();

        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

Answer 1

至少，您可以将读取-发送-接收逻辑包装在一个循环中：

while (true) {

    Console.WriteLine("Enter a message string: \n");

    message = Console.ReadLine();
    if (message == "quit") break;

    // Send test data to the remote device.  
    Send(client, message + "\r\n");  // \r\n required for server to know end of string
    sendDone.WaitOne();

    // Receive the response from the remote device.  
    Receive(client);
    receiveDone.WaitOne();

    // Write the response to the console.  
    Console.WriteLine("Response received : {0}", response);
}

我还建议您学习如何使用 Task asynchronous programming (TAP) 模型，这是新开发的推荐方法。 TAP 使用 async 和 await 关键字，以及 Task 类，以简洁、可读的方式实现异步。