package core;import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;class SocketServer {// Socket服务器端private int port; // 端口号public SocketServer(int port) {this.port = port;start();}private void start() {// 启动服务器端的方法try {ServerSocket serverSocket = new ServerSocket(port);// 根据端口创建服务器System.out.println("服务器已启动，监听端口号为：" + port);System.out.println("正在等待客户端连接。。。。。");Socket socketAccept = serverSocket.accept();// 挂起等待客户的请求BufferedReader in = new BufferedReader(new InputStreamReader(socketAccept.getInputStream()));// 获得（读取客户端的数据流）PrintWriter out = new PrintWriter(socketAccept.getOutputStream(), true); // 获得写往客户端的(数据输出流),true表示自动刷新out.println("服务器端连接成功。。。。");out.println("输入exit断开与服务器的连接");boolean done = false;while (!done) {String line = in.readLine();// 读取客户端每行的内容//System.out.println("line : "+line);if (line == null)done = true;else {System.out.println("客户端传来的内容： " + line);String message = infoUpperCase(line);// 变成大写再传回客户端去out.println("从服务器端口发送的内容 "+message); //--该处的print要加ln，否则就会无法往客户端传递消息if (line.trim().equals("exit")) // 退出判断done = true;}}socketAccept.close();  //关闭通信资源} catch (IOException e) {System.out.println("启动服务器端出现错误："+e.getMessage());}}public String infoUpperCase(String line) {return line.toUpperCase(); // 将字符串大写}
}public class TextSocketServer {public static void main(String[] args) {try {SocketServer server=new SocketServer(8080);} catch (Exception e) {System.out.println("测试服务器端监听出错: "+e.getMessage());}}
}

客户端程序

package core;import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;class Client { // Socket客户端private String host; // IP地址private int port; // 端口号public Client(String host, int port) {this.host = host;this.port = port;connectSocket();// 调用连接方法}public void connectSocket() {Socket socketConn; // 声明客户端的Socket连接try {if (host.equals("localhost") || host.equals("127.0.0.1")) {// 判断IP地址(域名)如果是本机localhostsocketConn = new Socket(InetAddress.getLocalHost(), port);// 创建本地Socket连接//如果该方法InetAddress.getLocalHost()报错，则要在sudo vi /private/etc/hosts 中添加本机地址与你主机名的映射，类似  127.0.0.1 主机名//然后终端执行命令 dscacheutil -flushcache，之后主机地址便可正常解析} else {socketConn = new Socket(InetAddress.getByName(host), port);// 创建远程socket连接}BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));// 获得从键盘输入的流PrintWriter out = new PrintWriter(socketConn.getOutputStream(), true);// 往服务器写内容的数据流// 从服务器获得信息BufferedReader in = new BufferedReader(new InputStreamReader(socketConn.getInputStream()));// 接收服务器发送内容的输入流System.out.println("服务器信息：" + in.readLine());System.out.println("服务器信息：" + in.readLine());System.out.println("请输入>");boolean done = false;while (!done) {String line = stdin.readLine();// 获得从键盘输入的每行字符out.println(line);// 发送到服务器端  --该处的print要加ln，否则就会无法往服务器端传递消息if (line.equalsIgnoreCase("exit")) // 读到exit则结束循环done = true;String info = in.readLine(); // 从服务器读取字符串System.out.println("服务器信息：" + info);// 显示从服务器发送来的数据if (!done)System.out.println("请输入>");}socketConn.close(); // 关闭资源} catch (SecurityException e) {System.out.println("连接服务器出现安全问题！"+e.getMessage());} catch (IOException e) {System.out.println("连接服务器出现I/O问题！"+e.getMessage());}}
}public class TextSocketClient {// Socket客户端类public static void main(String[] args) {try {new Client("localhost", 8080); // IP地址为本机，端口为8080} catch (Exception e) {System.out.println("测试客户端连接出错：" + e.getMessage());}}
}

客户端程序运行截图

socketConn = new Socket(InetAddress.getLocalHost(), port);// 创建本地Socket连接

                                String line = stdin.readLine();// 获得从键盘输入的每行字符out.println(line);// 发送到服务器端  --该处的print要加ln，否则就会无法往服务器端传递消息