JMS TopicSubscriber blocks on receive()

[Greg Matthews]

dear all,   i've having trouble with a subscriber blocking on a receive message call.   for the time being i can use a Queue instead of a Topic but would like to know if anyone can spot any stupid error i'm making.   --- code for publisher ----   Topic t = (Topic)ServerUtil.get( "jms/configTopic" ); TopicConnectionFactory tcf = (TopicConnectionFactory)ServerUtil.get( "jms/TopicConnectionFactory" ); TopicConnection tc = tcf.createTopicConnection(); TopicSession ts = tc.createTopicSession(false,TopicSession.AUTO_ACKNOWLEDGE); TopicPublisher tp = ts.createPublisher(t); Message m = ts.createTextMessage("hello world"); tp.publish(m);   // create subscriber in a new thread. new Thread( new Listener(tc,ts,t)).start();   ---- code for subscriber ----   class Listener implements Runnable {    TopicConnection tc;  TopicSession ts;  Topic t;    Listener(TopicConnection tc, TopicSession ts, Topic t) throws Exception {     this.tc= tc;   this.ts = ts;   this.t = t;  }  public void run() {      try {         TopicSubscriber sub = ts.createSubscriber(t,null,true);    System.out.println("receiving message..." );    tc.start();    synchronized(this) {     wait(5000);    }    System.out.println(sub.receive());        // <==== this line blocks. why?     } catch( Exception e ) {      e.printStackTrace();   }   System.out.println("end");  } }   thanks, greg.