Socket的Hello World程序

实现一个socket的hello world程序需要一个服务端一个客户端，服务端建立监听，客户端去访问，当然通信是相互的，客户端也可以向服务端发送信息！这里我敲了一个例子是客户端访问服务端，服务端返回一个Hello World!!

import java.io.IOException;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class SocketServerStudy {
    public static void main(String[] args) throws IOException {
         ServerSocket serverSocket = null;
         PrintWriter out = null;
         try {
             //实例一个socket服务端实例
            serverSocket = new ServerSocket(6666);
        } catch (IOException e) {
            System.out.println("实例化服务端失败"+e);
            System.exit(1);
        }
         Socket clientsocket =null;
         try {
             //监听客户端的连接
            clientsocket = serverSocket.accept();
        } catch (IOException e) {
            System.out.println("创建监听失败"+e);
            System.exit(1);
        }
        try {
            out = new PrintWriter(clientsocket.getOutputStream(),true);
            out.println("hello world!!!!");
        } catch (IOException e) {
            System.out.println("获取客户端输出流(写)失败");
            System.exit(1);
        }
        
        clientsocket.close();
        serverSocket.close();
        
         
        
    }
}

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket;
import java.net.UnknownHostException;

public class SocketClientStudy {
    public static void main(String[] args) throws IOException {
        Socket clientSocket = null;
        BufferedReader in = null;
        try {
            clientSocket = new Socket("localhost", 6666);
            in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
        } catch (UnknownHostException e) {
            System.out.println("解析网址错误");
            e.printStackTrace();
        } catch (IOException e) {
            System.out.println("连接拒绝：服务器未启动");
            e.printStackTrace();
        }
        System.out.println(in.readLine());
        in.close();
        clientSocket.close();
        
      }
}

 需要注意的是：需要先启动服务端，然后再启动客户端，否则是会报java.net.ConnectException: Connection refused: connect （拒绝连接）