案例 1

• 编写一个服务器端和一个客户端；
• 服务器端在 9999 端口监听；
• 客户端连接到服务端，发送“hello, server”，然后退出；
• 服务器端接收到客户端发送的信息，输出到控制台，并退出；

Server 端

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
public class Server {
    public static void main(String[] args) throws Exception {
        // 监听 9999 端口
        int port = 9999;
        ServerSocket serverSocket = new ServerSocket(port);
        // 建立连接
        Socket socket = serverSocket.accept();
        // 使用包装流包装一个字符流对象出来
        InputStream inputStream = socket.getInputStream();
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
        // 读取一行
        String line = null;
        line = bufferedReader.readLine();
        System.out.println(line);
        // 使用包装流包装一个字符流对象出来
        OutputStream outputStream = socket.getOutputStream();
        BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream));
        // 写入一行内容
        bufferedWriter.write("hello, client - 字符流");
        bufferedWriter.newLine();
        bufferedWriter.flush();
        // 关闭流和 socket
        bufferedReader.close();
        bufferedWriter.close();
        socket.close();
        serverSocket.close();
    }
}

Client 端

import java.io.*;
import java.net.InetAddress;
import java.net.Socket;
public class Client {
    public static void main(String[] args) throws Exception {
        int port = 9999;
        Socket socket = new Socket(InetAddress.getLocalHost(), port);
        OutputStream outputStream = socket.getOutputStream();
        BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream));
        Thread.sleep(3000);
        bufferedWriter.write("hello, server - 字符流示例");
        bufferedWriter.newLine();//插入一个换行符，表示写入内容结束，注意，此时要求对方使用 readLine() ！！！
        bufferedWriter.flush();// 如果使用的字符流，需要手动刷新，否则数据不会写入数据通道
        InputStream inputStream = socket.getInputStream();
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
        // 按行读取
        String line = null;
        line = bufferedReader.readLine();
        System.out.println(line);
        bufferedWriter.close();
        bufferedReader.close();
        socket.close();
    }
}