java - Multicast packets come in dirty -

i'm making simple multicast application controller locks , unlocks station via simple messages. controller , station both have receiver threads. reason, when first message sent, received well, when second message sent, received incorrectly, of first message attached it.

for example,

station 1 sends "locked: 1001" message. controller receives message correctly. controller sends "unlock: 1001" message. station 1 receives "unlock: 1ocked: 1001" 

here's station's receiver:

public class votingstationreceiver implements runnable{     private dummyvotingstation votingstation;     private multicastsocket s;     private thread listener = new thread(this);      public votingstationreceiver(multicastsocket s, dummyvotingstation votingstation){         this.s = s;         this.votingstation = votingstation;          listener.start();     }      public void run() {         byte[] buf = new byte[1024];          while(true)              try {                  datagrampacket pack = new datagrampacket(buf, buf.length);                 s.receive(pack);                 string msg = "";                 msg = new string(pack.getdata());                 msg = msg.trim();                  system.out.println(msg);                 system.out.println("voting station: message received");                  votingstation.processmessage(msg);              } catch(ioexception e) {                      break;              }      }  } 

and here's controller's message sent:

    private string unlockmsg = "unlock: ";     public void unlockstation(int lockedid) {         //send packet telling station unlock         string completemsg = unlockmsg+lockedid;         byte buf[] = completemsg.getbytes();          // create , send datagrampacket         datagrampacket pack;         try {             pack = new datagrampacket(buf, buf.length,                     inetaddress.getbyname(group), port);             int ttl = s.gettimetolive();             s.settimetolive(ttl);             s.send(pack);             system.out.println("control station: message sent");         } catch (unknownhostexception e) {             // todo auto-generated catch block             e.printstacktrace();         }         catch (ioexception e) {             e.printstacktrace();         }     } } 

i know beginner's problem, don't have experience multicasting , networking in general.

i suspect problem you're receiving datagram existing buffer that's had data in previous datagram receipt. try using new byte[] each receive. think need consider length of data coming in , consequently check out this answer make use of pack.getlength()