利用多线程、网络编程设计一个聊天程序。要求通过监听指定的端口号、目标IP地址和目标端口号，实现消息的发送和接收功能，并把聊天内容显示出来。 Java 代码实现

以下是一个简单的基于Java的多线程、网络编程聊天程序实现：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class ChatServer {
    public static final int PORT = 10086;
    private ServerSocket serverSocket;

    public ChatServer() throws IOException {
        serverSocket = new ServerSocket(PORT);
    }

    public void service() {
        while (true) {
            Socket socket = null;
            try {
                socket = serverSocket.accept();
                System.out.println("New client connected : " + socket.getInetAddress() + ":" + socket.getPort());
            } catch (IOException e) {
                e.printStackTrace();
            }

            // Start a new thread for the client
            Thread t = new Thread(new ClientHandler(socket));
            t.start();
        }
    }

    private static class ClientHandler implements Runnable {
        private Socket socket;
        private BufferedReader in;
        private PrintWriter out;

        public ClientHandler(Socket socket) {
            this.socket = socket;
            try {
                in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                out = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()));
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        public void run() {
            try {
                while (true) {
                    String str = in.readLine();
                    if (str == null) {
                        break;
                    }
                    System.out.println("Received from client: " + str);
                    out.println("Server received: " + str);
                    out.flush();
                }
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public static void main(String[] args) throws IOException {
        ChatServer server = new ChatServer();
        server.service();
    }
}

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Scanner;

public class ChatClient {
    public static final String SERVER_IP = "localhost";
    public static final int SERVER_PORT = 10086;
    private Socket socket;
    private BufferedReader in;
    private PrintWriter out;

    public ChatClient() throws IOException {
        socket = new Socket(SERVER_IP, SERVER_PORT);
        in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        out = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()));
    }

    public void service() {
        Scanner scanner = new Scanner(System.in);
        try {
            while (true) {
                String str = scanner.nextLine();
                if (str.equals("bye")) {
                    break;
                }
                out.println(str);
                out.flush();
                String echo = in.readLine();
                System.out.println(echo);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                socket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) throws IOException {
        ChatClient client = new ChatClient();
        client.service();
    }
}

可以在不同的控制台窗口中启动多个聊天客户端，它们将连接到服务器并通过向服务器发送消息来进行交互。服务器将显示接收到的消息，并将回应发送回客户端。