基于UDP实现用户数据互传案例

柔光的暖阳◎ 2023-10-17 15:04 109阅读 0赞

UDP--User Datagram Protocol,用户数据报协议.是一个无连接的协议,以数据报文单位进行数据传输,每个数据报是一个独立信息,其中包括目标主机IP地址和端口.

主要用到了DatagramSocket类和DatagramPacket类来实现

UDP特点:

1)将数据及源和目的封装成数据包中，不需要建立连接  
2)每个数据报的大小在限制在64k内  
3)因无连接，是不可靠协议  
4)不需要建立连接，速度快

实现步骤:

1)DatagramSocket与DatagramPacket  
2)建立发送端，接收端。  
3)建立数据包。  
4)调用Socket的发送接收方法。  
5)关闭Socket。  
发送端与接收端是两个独立的运行程序。

☆发送端

在发送端，要在数据包对象中明确目的地IP及端口。

DatagramSocket ds = new DatagramSocket();
    byte[] by = “hello,udp”.getBytes();
    DatagramPacket dp = new DatagramPacket(by,0,by.length,
    	InetAddress.getByName(“127.0.0.1”),10000);
    ds.send(dp);
    ds.close();

☆接收端

在接收端，要指定监听的端口。

DatagramSocket ds = new DatagramSocket(10000);
    byte[] by = new byte[1024];
    DatagramPacket dp = new DatagramPacket(by,by.length);
    ds.receive(dp);
    String str = new String(dp.getData(),0,dp.getLength());
    System.out.println(str+"--"+dp.getAddress());
    ds.close();

实战 练习：UDP聊天程序

1)通过键盘录入获取要发送的信息。  
2)将发送和接收分别封装到两个线程中。

路人甲:

package cn.hucu.UDP.udp.chat.one;
    
    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;
    
    public class UDPChat {
    	public static void main(String[] args) throws IOException {
    		//1创建ds--socket
    		//如果空参数,由系统随便给我们分配一个端口号发送--凡是socket通讯都要有端口号
    		DatagramSocket send = new DatagramSocket(10003);
    		DatagramSocket receive = new DatagramSocket(10004);
    		new Thread(new Send(send)).start();   //使用线程
    		new Thread(new Receive(receive)).start();
    	}
    
    }
    
    class Send implements Runnable {
    	private DatagramSocket ds;
    
    	public Send(DatagramSocket ds) {
    		this.ds = ds;
    	}
    
    	@Override
    	public void run() {
    		// 源:System.in
    		// 目的:socket + dp
    		BufferedReader br = null;
    		try {
    			br = new BufferedReader(new InputStreamReader(System.in));
    			String line = null;
    			while ((line = br.readLine()) != null) {
    				//2创建dp--数据包
    				byte buf[] = line.getBytes();
    				DatagramPacket dp = new DatagramPacket(buf, buf.length,
    						InetAddress.getByName("127.0.0.1"), 10002); // 改成对方IP
    				//3发送  ---选用socket把数据包发送出去
    				ds.send(dp);
    				if ("over".equalsIgnoreCase("line")) {
    					break;
    				}
    			}
    			//4关流
    			ds.close();
    		} catch (IOException e) {
    			e.printStackTrace();
    		} finally{
    			if(ds!=null){
    				ds.close();
    			}
    			if(br!=null){
    				try {
    					br.close();
    				} catch (IOException e) {
    					throw new RuntimeException("关流失败,很危险!");
    				}
    			}
    		}
    	} 
    }
    
    class Receive implements Runnable {
    	private DatagramSocket ds;
    
    	public Receive(DatagramSocket ds) {
    		this.ds = ds;
    	}
    
    	@Override
    	public void run() {
    		byte buf[] = new byte[512];
    		try {		
    			DatagramPacket dp = new DatagramPacket(buf, buf.length);
    			ds.receive(dp);
    
    			// 解析数据包
    			//4从dp中把数据解析出来----获取对方的ip
    			String ip = dp.getAddress().getHostAddress();// 记录发送方的IP地址
    			String str = new String(dp.getData(), 0, dp.getLength());
    			System.out.println(ip + "说:" + str);
    			if ("Over".equalsIgnoreCase(str)) {
    				System.out.println(ip + "离开聊天室....");
    			}
    		} catch (IOException e) {
    			e.printStackTrace();
    		}
    	}
    
    }

路人乙:

package cn.hucu.UDP.udp.chat.two;
    
    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;
    
    public class UDPChat {
    	public static void main(String[] args) throws IOException {
    		DatagramSocket send = new DatagramSocket(10001);
    		DatagramSocket receive = new DatagramSocket(10002);
    		new Thread(new Send(send)).start();
    		new Thread(new Receive(receive)).start();
    	}
    }
    
    class Send implements Runnable {
    	private DatagramSocket ds;
    
    	public Send(DatagramSocket ds) {
    
    		this.ds = ds;
    	}
    
    	@Override
    	public void run() {
    		BufferedReader br = null;
    		try {
    			br = new BufferedReader(new InputStreamReader(System.in));
    			String line = null;
    			while ((line = br.readLine()) != null) {
    				byte buf[] = new byte[512];
    				DatagramPacket dp = new DatagramPacket(buf, buf.length,
    						InetAddress.getByName("192.168.0.1"), 10004); //IP要改成对方的IP
    				ds.send(dp);
    				if ("voer".equalsIgnoreCase("line")) {
    					break;
    				}
    			}
    		} catch (IOException e) {
    			e.printStackTrace();
    		} finally {
    			if (br != null) {
    				try {
    					br.close();
    				} catch (IOException e) {
    					throw new RuntimeException("关流失败!!");
    				}
    				if (ds != null) {
    					ds.close();
    				}
    
    			}
    		}
    
    	}
    }
    
    class Receive implements Runnable {
    	private DatagramSocket ds;
    
    	public Receive(DatagramSocket ds) {
    		this.ds = ds;
    	}
    
    	@Override
    	public void run() {
    		byte buf[] = new byte[512];
    		try {
    
    			DatagramPacket dp = new DatagramPacket(buf, buf.length);
    			ds.receive(dp);
    
    			// 解析数据包
    			String ip = dp.getAddress().getHostAddress();
    			// int port = dp.getPort(); 获取端口号
    			String str = new String(dp.getData(), 0, dp.getLength());
    
    			System.out.println(ip + "说:" + str);
    			if ("Over".equalsIgnoreCase(str)) {
    				System.out.println(ip + "离开聊天室....");
    			}
    		} catch (IOException e) {
    			e.printStackTrace();
    		}
    
    	}
    
    }

这里应该是不够完善的,不过会再改进!!!!!