基于socket实现的TCP Client 异步通讯代码 C#

在 C# 中实现基于 socket 的 TCP Client 异步通信，通常会使用 `System.Net.Sockets` 命名空间下的 `Socket` 类，并利用异步方法如 `BeginConnect`, `EndConnect`, `BeginReceive`, `EndReceive`, `BeginSend`, `EndSend` 等来完成。以下是一个简单的例子，展示了如何实现一个基本的异步 TCP Client。

首先，需要引入必要的命名空间：

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;

然后，创建一个 TCP Client 类，包含连接、接收和发送数据的方法：

public class TcpAsyncClient
{
    private Socket clientSocket;
    private string serverIp;
    private int serverPort;

    public TcpAsyncClient(string ip, int port)
    {
        serverIp = ip;
        serverPort = port;
        clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
    }

    public void ConnectAsync()
    {
        try
        {
            clientSocket.BeginConnect(new IPEndPoint(IPAddress.Parse(serverIp), serverPort), new AsyncCallback(ConnectCallback), clientSocket);
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

    private void ConnectCallback(IAsyncResult ar)
    {
        try
        {
            Socket client = (Socket)ar.AsyncState;
            client.EndConnect(ar);
            Console.WriteLine("Connected to server...");

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

    private void ReceiveMessage(Socket client)
    {
        try
        {
            byte[] buffer = new byte[1024];
            client.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(ReceiveCallback), buffer);
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

    private void ReceiveCallback(IAsyncResult ar)
    {
        try
        {
            byte[] buffer = (byte[])ar.AsyncState;
            int bytesRead = clientSocket.EndReceive(ar);
            if (bytesRead > 0)
            {
                string receivedData = Encoding.UTF8.GetString(buffer, 0, bytesRead);
                Console.WriteLine("Received: " + receivedData);

                // Send data back as echo or handle the received data accordingly
                // EchoMessage(client, receivedData);
            }
            else
            {
                Console.WriteLine("Connection closed.");
                return;
            }

            // Continue to receive messages
            ReceiveMessage(clientSocket);
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

    public void SendMessage(string message)
    {
        try
        {
            byte[] messageBytes = Encoding.UTF8.GetBytes(message);
            clientSocket.BeginSend(messageBytes, 0, messageBytes.Length, SocketFlags.None, new AsyncCallback(SendCallback), clientSocket);
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

    private void SendCallback(IAsyncResult ar)
    {
        try
        {
            Socket client = (Socket)ar.AsyncState;
            int bytesSent = client.EndSend(ar);
            Console.WriteLine("Sent " + bytesSent + " bytes to server.");
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

    public void Close()
    {
        if (clientSocket.Connected)
        {
            clientSocket.Shutdown(SocketShutdown.Both);
            clientSocket.Close();
        }
    }
}

使用该类的示例：

class Program
{
    static void Main(string[] args)
    {
        TcpAsyncClient client = new TcpAsyncClient("127.0.0.1", 12345);

        client.ConnectAsync();

        // 在接收到数据时，可以调用 SendMessage 发送消息
        // client.SendMessage("Hello, Server!");

        Console.WriteLine("Press any key to exit...");
        Console.ReadKey();

        client.Close();
    }
}

这段代码演示了如何异步连接服务器，接收数据以及发送数据。请注意，这个例子使用了同步方法的回调版本来处理异步操作，并且简单地实现了回声（echo）功能，即收到什么消息就发送什么消息。在实际应用中，你可能需要根据业务逻辑来处理接收到的数据和发送的消息。