Java UDP Broadcast code sample

Application scenario: A school, whenever the time is over to provide tips for the class function.

Analysis: The use of UDP to achieve broadcast to the same network segment of the computer to send data, the client received the data, Pop-up prompts dialog box. The service side needs a loop to determine whether the time is over, if you use the dead loop here, very much of the system resources, I tested the cup in 100%, with Java Timer class can be a good solution to this problem, not only to ensure that the program is always running, and does not account for system resources, specific principles, not carefully studied. Here's a look at the code implementation

Service Segment Code:

Import java.io.IOException; Import Java.net.DatagramPacket; Import Java.net.DatagramSocket; Import java.net.InetAddress; Import java.net.SocketException; Import java.net.UnknownHostException; Import Java.text.SimpleDateFormat; Import Java.util.Date; Import Java.util.Timer; public class Udpsend {public void SendData () throws SocketException, unknownhostexception{datagramsocket ds = new Datagra Msocket ();//create socket string str = "1" to send datagram packets; Datagrampacket DP = new Datagrampacket (Str.getbytes (), str.getbytes (). Length, Inetaddress.getbyname ("255.255.255.255 "), 3001); Constructs a datagram package that is used to send packets of length to the specified port number on the specified host to try {Ds.send (DP);} catch (IOException e) {e.printstacktrace ();} ds.close (); public static void Main (string[] args {Timer timer = new timer (); Timer.schedule (new MyTask (), 1000, 1000);} static C Lass MyTask extends java.util.timertask{@Override public void Run () {udpsend TT = new Udpsend (); Date d = new Date (); SimpleDateFormat SDF = new SimpleDateFormat ("HH:mm:ss"); String STRDate = Sdf.format (d); String[] Classtime = {"17:18:00", "17:19:00", "17:20:00"}; for (int i = 0;i<classtime.length;i++) {if (Classtime[i].equals (strdate)) {try {tt.senddata ();} catch ( SocketException e) {//Todo auto-generated catch block E.printstacktrace ();} catch (Unknownhostexception e) {//Todo Au To-generated Catch block E.printstacktrace (); } } } } } }

Customer single Simple code example, no loops

Package UDP; Import Java.net.DatagramPacket; Import Java.net.DatagramSocket; public class Udprecv {public static void main (string[] args) throws Exception {datagramsocket ds = new Datagramsocket (30 01)//Create a Receive datagram socket and bind it to the specified port on the local host byte[] buf = new byte[1024]; Datagrampacket DP = new Datagrampacket (buf, 1024); Ds.receive (DP); String strrecv = new String (Dp.getdata (), 0, Dp.getlength ()) + "from" + dp.getaddress (). Gethostaddress () + ":" + DP.GETP ORT (); System.out.println (STRRECV); Ds.close (); } }