public class SendMes extends Thread {public void run() {// 覆写Thread类中的run方法try {while (true) {DatagramSocket socket = new DatagramSocket(2425);byte[] buffer = new byte[65508];DatagramPacket packet = new DatagramPacket(buffer, 0,buffer.length);socket.receive(packet);socket.close();String s = new String(packet.getData(), 0, packet.getLength());String[] strs = s.split(":");System.out.println(strs[4]);if (strs.length > 4 && strs[4].equals("6291457")) {// System.out.println("用户上线了");long IPMSG_SENDMSG = 0x00000020;String address = packet.getAddress().toString().substring(1);String HOST = "系统管理员";String SENDER = "系统管理员";String MSG_CONTENT = "您好,您有一封邮件未处理";DatagramSocket socket1 = new DatagramSocket();byte[] buffer1 = ("1:" + new Date().getTime() + ":"+ SENDER + ":" + HOST + ":" + IPMSG_SENDMSG + ":" + MSG_CONTENT).getBytes("gbk");// 版本号:报文编号:发送者:ip:命令:内容DatagramPacket packet1 = new DatagramPacket(buffer1,buffer1.length, packet.getAddress(), 2425);socket1.send(packet1); // 发送报文socket1.close();System.out.println("send message is ok.");}if (strs.length > 4 && strs[4].equals("6291458")) {System.out.println("用户下线了");}}} catch (SocketException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}} 发现局域网内飞秋用户上线,自动发送自定义聊天内容!