java socket

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {

	/** 端口号 */
	public static final int PORT = 9999;

	public static void main(String[] args) {
		System.out.println("服务器...\n");
		Server ser = new Server();
		ser.sock();
	}

	public void sock() {
		try {
			ServerSocket server = new ServerSocket(PORT);
			while (true) {
				// 一旦有堵塞, 则表示服务器与客户端获得了连接
				Socket client = server.accept();
				// 处理这次连接
				new PServer(client);
			}
		} catch (Exception e) {
			System.out.println("服务器异常: " + e.getMessage());
		}
	}

	private class PServer implements Runnable {

		private Socket socket;

		public PServer(Socket sock) {
			socket = sock;
			new Thread(this).start();
		}

		public void run() {
			try {
				// 读取客户端数据
				DataInputStream input = new DataInputStream(socket.getInputStream());
				// 向客户端发送数据
				DataOutputStream out = new DataOutputStream(socket.getOutputStream());
				
				// 读取客户端数据
				System.out.println("客户端发过来的内容: " + input.readUTF());

				System.out.print("请输入: \t");
				// 发送键盘输入的一行
				String s = new BufferedReader(new InputStreamReader(System.in)).readLine();
				out.writeUTF(s);

				input.close();
				out.close();
			} catch (Exception e) {
				System.out.println("服务器 run 异常: " + e.getMessage());
			}
		}

	}

}

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.net.Socket;

public class Client {
	
	/** 端口号 */
	public static final int PORT = 9999;
	
	/** ip 地址 */
	public static final String IP = "localhost";
	
	public static void main(String[] args) {
		System.out.println("客户端...");
		Socket socket = null;
		try {
			System.out.println("当接收到服务器端字符为 \"好\" 的时候, 客户端将终止\n");
			while (true) {
				// 创建一个流套接字并将其连接到指定主机上的指定端口号
				socket = new Socket(IP, PORT);
				
				// 读取服务器端数据
				DataInputStream input = new DataInputStream(socket.getInputStream());
				// 向服务器端发送数据
				DataOutputStream out = new DataOutputStream(socket.getOutputStream());

				System.out.print("请输入: \t");
				String str = new BufferedReader(new InputStreamReader(System.in)).readLine();
				out.writeUTF(str);
				
				String ret = input.readUTF(); 
				System.out.println("服务器端返回过来的是: " + ret);
				// 如接收到 "好" 则断开连接
				if ("好".equals(ret)) {
					System.out.println("客户端将关闭连接");
					Thread.sleep(500);
					break;
				}
			}
		} catch (Exception e) {
			System.out.println("客户端异常: " + e.getMessage());
		} finally {
			if (socket != null) {
				try {
					socket.close();
				} catch (Exception e) {
					socket = null;
					System.out.println("客户端 finally 异常: " + e.getMessage());
				}
			}
		}
	}

}