Push Registry Activation by SMS

[Le Ngoc Quoc Khanh]

I used the "Companion Code" at http://developers.sun.com/techtopics/mobility/midp/articles/pushreg/ to test push technology in MIDP 2.0.
I have customized it a little to support SMS like this:

  
public class BasicPushMIDlet extends MIDlet implements CommandListener,
Runnable {
    //  Default values to use.
    String midletClassName = this.getClass().getName();
    String defaultURL = "sms://:50000";
 
...
 
class PushProcessor implements Runnable {
...
   public void run() {
      if (url.startsWith("socket://")) {
      ...
      } else if (url.startsWith("datagram://")) {
      ...
      } else if (url.startsWith("sms://")) {
         System.out.println("Starts with sms");
         mc = (MessageConnection)Connector.open(url);
         TextMessage tm = (TextMessage)mc.receive();
         System.out.println(tm.getPayloadText());
      }
...

When tested OTA and sent an "Hello from SMS" message to port 50000, I encountered IOException:

Setting up...
is PushActivated
[B]Starts with sms[/B]
Hello from SMS
[B]Starts with sms[/B]
PushProcessor.run Exceptionjava.io.IOException: Already opened
java.io.IOException: Already opened
at com.sun.midp.io.j2me.sms.Protocol.openPrimInternal(+528)
at com.sun.midp.io.j2me.sms.Protocol.openPrim(+8)
at javax.microedition.io.Connector.openPrim(+233)
at javax.microedition.io.Connector.open(+15)
at javax.microedition.io.Connector.open(+6)
at javax.microedition.io.Connector.open(+5)
at j2medeveloper.basicpush.BasicPushMIDlet$PushProcessor.run(+224)

My questions are:
1. Why I have two "Starts with sms" strings?
2. What is the mecharnism when a MIDlet is activated by SMS. Why other connections did not encounter this IOException?