java客户端和服务器端如何给别人发消息

Java客户端和服务器端可以使用Socket编程来实现消息发送和接收。以下是一个简单的例子：

客户端发送消息：

Socket socket = new Socket("服务器IP地址", 8888);
OutputStream outputStream = socket.getOutputStream();
outputStream.write("Hello, Server!".getBytes());
socket.close();

服务器端接收消息：

ServerSocket serverSocket = new ServerSocket(8888);
Socket socket = serverSocket.accept();
InputStream inputStream = socket.getInputStream();
byte[] buffer = new byte[1024];
int len = inputStream.read(buffer);
String message = new String(buffer, 0, len);
System.out.println("Received message: " + message);
socket.close();

以上代码演示了客户端向服务器端发送消息，服务器端接收消息并打印出来。实际中，可以根据具体需求进行修改和扩展。

相关问题

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。

java客户端登陆服务器用户名验证客户端和服务器端的代码演示

好的，以下是一个简单的 Java 客户端和服务器端的演示代码，用于验证客户端登陆服务器的用户名：

## 服务器端代码

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

public class Server {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(9999);
        System.out.println("服务器已启动，等待客户端连接...");

        while (true) {
            Socket socket = serverSocket.accept();
            System.out.println("客户端已连接，地址：" + socket.getRemoteSocketAddress());

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

            String username = in.readLine();

            if (username.equals("admin")) {
                out.println("欢迎登陆！");
            } else {
                out.println("用户名不正确！");
            }

            socket.close();
        }
    }
}

## 客户端代码

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

public class Client {
    public static void main(String[] args) throws IOException {
        Socket socket = new Socket("localhost", 9999);

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

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("请输入用户名：");
        String username = br.readLine();

        out.println(username);

        String response = in.readLine();
        System.out.println(response);

        socket.close();
    }
}

以上代码实现了一个简单的用户名验证功能，当客户端输入用户名后，向服务器发送用户名，服务器接收后判断是否为 "admin"，如果是，则返回欢迎信息，否则返回错误信息。