网络编程—UDP与URL

网络编程—UDP
发消息：不用连接；需要知道对方的地址！

发送消息
客户端

package com.deng.lesson03;
​
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
​
//不需要连接服务器
public class UdpClientDemo01 {
   public static void main(String[] args) throws Exception{
       //1.建立一个Socket
       DatagramSocket socket = new DatagramSocket();
       //2.建个包
       String msg = "你好，欢迎光临";
       //发送给谁
       InetAddress localhost = InetAddress.getByName("localhost");
       int port = 9090;
       //数据 数据的长度起始 要发送给谁
       DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length,localhost,port);
       //3.发送包
       socket.send(packet);
       //4.关闭流
       socket.close();
  }
}

服务端

package com.deng.lesson03;
​
import java.net.DatagramPacket;
import java.net.DatagramSocket;
​
public class UdpServerDemo01 {
   public static void main(String[] args) throws Exception{
       //开放端口
       DatagramSocket socket= new DatagramSocket(9090);
       //接受数据包
       byte[] buffer = new byte[1024];
       DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);
​
       socket.receive(packet);//阻塞接受
​
       System.out.println(packet.getAddress().getHostAddress());
       System.out.println(new String(packet.getData(),0,packet.getLength()));
       //关闭连接
       socket.close();
  }
}

咨询
循环发送消息
package com.deng.chat;
​
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
​
//发送方
public class UdpSenderDemo01 {
   public static void main(String[] args) throws Exception{
       DatagramSocket socket = new DatagramSocket(8888);
​
       //准备数据 控制台System.in
       BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
​
       while (true){
           String data = reader.readLine();
           byte[] datas = data.getBytes();
           DatagramPacket packet = new DatagramPacket(datas,0,datas.length,new InetSocketAddress("localhost",6666));
           socket.send(packet);
           if (data.equals("bye")){
               break;
          }
      }
       socket.close();
  }
}
循环接收消息
package com.deng.chat;
​
import java.net.DatagramPacket;
import java.net.DatagramSocket;
​
//接收方
public class UdpReceiveDemo01 {
   public static void main(String[] args) throws  Exception{
       DatagramSocket socket = new DatagramSocket(6666);
       while (true){
        //准备接受包裹
      byte[] container = new byte[1024];
      DatagramPacket packet = new DatagramPacket(container, 0, container.length);
      socket.receive(packet);//阻塞式接受包裹
​
      //断开连接 bye
      byte[] data = packet.getData();
      String receiveData = new String(data, 0, data.length);
      System.out.println(receiveData);
      if (receiveData.equals("bye")){
          break;
        }
      }
      socket.close();
  }
}

在线咨询： 两个人都可以是发送方 都可以是接收方
建一个TalkReceive

package com.deng.chat;
​
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
​
public class TalkReceive implements Runnable{
​
   DatagramSocket socket = null;
   private int port;
   private String msgFrom;
​
   public TalkReceive(int port,String msgFrom) {
       this.port = port;
       this.msgFrom =msgFrom;
       try {
           socket = new DatagramSocket(port);
      } catch (SocketException e) {
           e.printStackTrace();
      }
  }
​
   @Override
   public void run() {
       while (true){
           try {
               //准备接受包裹
               byte[] container = new byte[1024];
               DatagramPacket packet = new DatagramPacket(container, 0, container.length);
               socket.receive(packet);//阻塞式接受包裹
​
               //断开连接 bye
               byte[] data = packet.getData();
               String receiveData = new String(data, 0, data.length);
​
               System.out.println(msgFrom +":"+receiveData);
​
               if (receiveData.equals("bye")){
                   break;
              }
          } catch (IOException e) {
               e.printStackTrace();
          }
      }
       socket.close();
  }
​
}
​
建一个TalkSend

package com.deng.chat;
​
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
import java.net.SocketException;
​
public class TalkSend implements Runnable{
   DatagramSocket socket = null;
   BufferedReader reader = null;
​
   private int fromPort;
   private String toIP;
   private int toPort;
   public TalkSend(int fromPor,String toIP,int toPort) {
       this.fromPort = fromPort;
       this.toIP = toIP;
       this.toPort = toPort;
​
       try {
           socket = new DatagramSocket(fromPort);
           reader = new BufferedReader(new InputStreamReader(System.in));
      } catch (SocketException e) {
           e.printStackTrace();
      }
  }
​
​
   @Override
   public void run() {
       try {
           while (true){
               String data = reader.readLine();
               byte[] datas = data.getBytes();
               DatagramPacket packet = new DatagramPacket(datas,0,datas.length,new InetSocketAddress(this.toIP,this.toPort));
               socket.send(packet);
               if (data.equals("bye")){
                   break;
              }
          }
      } catch (IOException e) {
           e.printStackTrace();
      }
       socket.close();
  }
}
建一个TalkSend

package com.deng.chat;
​
public class TalkSend {
   public static void main(String[] args) {
       //开启两个线程
       new Thread(new TalkSend(7777,"localhost",9999)).start();
       new Thread(new TalkReceive(8888,"老师")).start();
  }
}
​
建一个TalkTeacher

package com.deng.chat;
​
public class TalkTeacher {
   public static void main(String[] args) {
       new Thread(new TalkSend(5555,"localhost",8888)).start();
       new Thread(new TalkReceive(9999,"学生")).start();
  }
}
​

URL
统一资源定位符：定位资源的，定位互联网上的某一个资源

DNS 域名解析 xxx.x..x..x

1.协议： //ip地址：端口/项目名/资源
例题：下载网络资源

package com.deng.lesson04;
​
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
​
//下载网络资源
public class urlDown {
​
   public static void main(String[] args) throws Exception{
       //1.下载地址
       URL url = new URL("https://s4.music.126.net/style/web2/img/default/default_avatar_40.jpg");
       //2.连接到这个资源 HTTP
       HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
​
       InputStream inputStream = urlConnection.getInputStream();
       FileOutputStream fos = new FileOutputStream("40.jpg");
​
       byte[] buffer = new byte[1024];
       int len;
       while ((len=inputStream.read(buffer))!=-1){
           fos.write(buffer,0,len);//写出数据
      }
       fos.close();
       inputStream.close();
       urlConnection.disconnect();//断开连接
  }
}