udp 局域网群聊

UDP：

无连接协议

udp协议发送数据，用的是数据报包的形式。(64KB以内)

发送端：

1.定义发送的datagramsocket对象，发送端可以不用定义端口

2.定义封装数据包datagrampacket

3.发送数据包

4.关闭资源

//InetAddress.getByName("192.168.3.255")必须是统一的网段

public class UdpSendThread implements Runnable {

	DatagramSocket ds;
	byte[] buf;

	public UdpSendThread(DatagramSocket ds) {
		this.ds = ds;
	}

	public UdpSendThread(DatagramSocket ds, String str) {

		this.ds = ds;
		this.buf = str.getBytes();
	}

	@Override
	public void run() {

		String brStr;
		try {
			BufferedReader br = new BufferedReader(new InputStreamReader(System.in, "utf-8"));

				while ((brStr = br.readLine()) != null) {

					if(brStr.startsWith("@")){

					}

					DatagramPacket dp = new DatagramPacket(brStr.getBytes(), brStr.getBytes().length,
							InetAddress.getByName("192.168.3.255"), 9000);

					ds.send(dp);
					if (brStr.equals("over")) {
						break;
					}

				}

			//br.close();
			ds.close();
		} catch (UnknownHostException | UnsupportedEncodingException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

接收端：

1、建立DatagramSocket对象

2、定义一个空的数据包

3、接受数据包

4、解析数据包

5、关闭资源

public class UdpRececiveThread extends Thread {

	DatagramSocket ds;

	public UdpRececiveThread(DatagramSocket ds) {

		this.ds = ds;
	}

	@Override
	public void run() {

		while(true){
			byte[] buf = new byte[1024*1024];
			DatagramPacket dp = new DatagramPacket(buf, buf.length);

			try {
				ds.receive(dp);
				String ip = dp.getAddress().getHostAddress();
				String content = new String(dp.getData(),0,dp.getLength());
				if(content.equals("over")){
					System.out.println(ip+"退出");
				}

				System.out.println(ip+":"+content);

			} catch (IOException e) {
				e.printStackTrace();
			}

		}
	}
}

　　测试类：

	public static void main(String[] args) throws SocketException {

		DatagramSocket sendDs = new DatagramSocket();
		DatagramSocket reDs = new DatagramSocket(9000);
	    new Thread(new UdpSendThread(sendDs)).start();;
		new UdpRececiveThread(reDs).start();
	}