[JXTA discuss] How can I get the peer Id?

hi!
I have a problem about how to get the peer Id of the JXME client.
the tutorial from the www.jxta.org mentions that:
 When a mobile client connects to a JXTA network, it first requests a peer identifier. The relay assigns a peer identifier in response to the request, and the client uses the peer identifier in subsequent communication.

So, I send a request from the client to the relay which is running on the same PC.The request is like this:
GET /unknown-unknown?0,-1,http://172.16.0.37:2481/
EndpointService:jxta-NetGroup/
uuid-DEADBEEFDEAFBABAFEEDBABE0000000F05/pid HTTP/1.1
Connection: close
Content-Length: 0
User-Agent: UNTRUSTED/1.0
Host: 172.16.0.37:2481


But, I never get a peer Id. 
I'd like to know what's the problem with it?
This problem bothers me a frew days,it will be appreciated if some can help me about this. Thks!