java客户端和服务器端

Java是一种面向对象的编程语言，可以用来开发客户端和服务器端应用程序。下面是一个简单的Java客户端/服务器端的例子：

服务器端：

import java.net.*;
import java.io.*;

public class Server {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = null;

        try {
            serverSocket = new ServerSocket(8080);
        } catch (IOException e) {
            System.err.println("Could not listen on port: 8080.");
            System.exit(1);
        }

        Socket clientSocket = null;
        try {
            System.out.println("Waiting for connection...");
            clientSocket = serverSocket.accept();
            System.out.println("Connection established!");
        } catch (IOException e) {
            System.err.println("Accept failed.");
            System.exit(1);
        }

        PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
        BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));

        String inputLine;

        while ((inputLine = in.readLine()) != null) {
            System.out.println("Received message: " + inputLine);
            out.println(inputLine);
        }

        out.close();
        in.close();
        clientSocket.close();
        serverSocket.close();
    }
}

客户端：

import java.io.*;
import java.net.*;

public class Client {
    public static void main(String[] args) throws IOException {

        Socket clientSocket = null;
        PrintWriter out = null;
        BufferedReader in = null;

        try {
            clientSocket = new Socket("localhost", 8080);
            out = new PrintWriter(clientSocket.getOutputStream(), true);
            in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
        } catch (UnknownHostException e) {
            System.err.println("Don't know about host: localhost.");
            System.exit(1);
        } catch (IOException e) {
            System.err.println("Couldn't get I/O for the connection to: localhost.");
            System.exit(1);
        }

        BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
        String userInput;

        while ((userInput = stdIn.readLine()) != null) {
            out.println(userInput);
            System.out.println("Server response: " + in.readLine());
        }

        out.close();
        in.close();
        stdIn.close();
        clientSocket.close();
    }
}

这个例子展示了一个简单的客户端/服务器端应用程序，服务器端绑定到本地8080端口并等待客户端连接，当客户端连接成功后，服务器端接收客户端发送的消息并将其原样返回给客户端。客户端连接到服务器端并发送消息，随后接收服务器端的响应消息并将其打印到控制台。