java__网络编程UDP

package cn.itcast.udp;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

/*
每个网络程序都有自己所处理的特定格式数据,如果接收到的数据不符合指定的格式，那么就会被当成垃圾数据丢弃。(加密..)

飞Q接收的数据格式：
version:time :sender : ip: flag:content ;
版本号          时间         发送人   :IP： 发送的标识符(32): 真正的内容;

在udp协议中，有一个IP地址称作为广播地址，广播地址就是主机号为255地址。

给广播IP地址发送消息的时候，在同一个网络段的机器都可以接收 到信息。
192.168.15.255

*/
//使用udp协议给飞Q发送消息。
public class FeiQDemo {

public static void main(String[] args) throws IOException {
// 建立udp的服务
DatagramSocket socket = new DatagramSocket();
// 准备数据，把数据封装到数据包中
String data = getData("feiQ你好！");
DatagramPacket packet = new DatagramPacket(data.getBytes(),
data.getBytes().length,
InetAddress.getByName("192.168.15.255"), 2425);
// 发送数据
socket.send(packet);
// 关闭资源
socket.close();

}

// 把数据拼接成指定格式的数据
public static String getData(String content) {
StringBuilder sb = new StringBuilder();
sb.append("1.0:");
sb.append(System.currentTimeMillis() + ":");
sb.append("习大大:");
sb.append("192.168.10.1:");
sb.append("32:");
sb.append(content);

return sb.toString();
}

}

package cn.itcast.udp;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;

//群聊发送端
public class ChatSender extends Thread {

@Override
public void run() {
try {
//建立udp的服务
DatagramSocket socket = new DatagramSocket();
//准备数据，把数据封装到数据包中发送
BufferedReader keyReader = new BufferedReader(new InputStreamReader(System.in));
String line = null;
DatagramPacket packet  = null;
while((line = keyReader.readLine())!=null){
//把数据封装 到数据数据包中，然后发送数据。
packet = new DatagramPacket(line.getBytes(), line.getBytes().length, InetAddress.getByName("192.168.15.255"), 9090);
//把数据发送出去
socket.send(packet);
}
//关闭 资源
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}

}

package cn.itcast.udp;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

//群聊接收端
public class ChatReceive extends Thread {

@Override
public void run() {
try {
//建立udp的服务,要监听一个端口
DatagramSocket socket = new DatagramSocket(9090);
//准备空的数据包存储数据
byte[] buf = new byte[1024];
DatagramPacket packet = new DatagramPacket(buf, buf.length);
boolean flag = true;
while(flag){
socket.receive(packet);
// packet.getAddress() 获取对方数据 包的IP地址对象。
System.out.println(packet.getAddress().getHostAddress()+"说:"+new String(buf,0,packet.getLength()));
}
//关闭资源
socket.close();

}catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

}

//开启线程的主程序
package cn.itcast.udp;

public class ChatMain {

public static void main(String[] args) {
ChatReceive chatReceive = new ChatReceive();
chatReceive.start();

ChatSender chatSender = new ChatSender();
chatSender.start();

}

}

package cn.itcast.udp;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.UnknownHostException;

/*
udp是一个不可靠（数据包可能会丢失）的协议

什么情况下数据包会出现丢失呢？
1.带宽不足 。
2.cpu的处理能力不足。

*/
public class SafeSender {

public static void main(String[] args) throws Exception {
//建立udp的服务
DatagramSocket socket = new DatagramSocket();
//准备数据，数据封装到数据中发送
DatagramPacket packet = null;
for(int i =  0 ; i< 10; i++){  //连续发送10个数据包
String data =i +"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
packet = new DatagramPacket(data.getBytes(), data.getBytes().length, InetAddress.getLocalHost(), 9090);
//发送数据包
socket.send(packet);
}
//关闭资源
socket.close();
}

}

package cn.itcast.udp;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class SafeReceive {

public static void main(String[] args) throws IOException, Exception {
//建立udp的服务
DatagramSocket socket = new DatagramSocket(9090);

//建立空的数据包存储数据
byte[] buf = new byte[1024];
DatagramPacket packet = new DatagramPacket(buf, buf.length);

//不断接收数据包
while(true){
socket.receive(packet);
System.out.println(new String(buf,0,packet.getLength()));
Thread.sleep(10);
}

}

}