Anyway, to know the phone's IP use method getLocalAddress() in ServerSocketConnection (or SocketConnection)
Also, according to the MIDP specs "The local hostname (if available) can be accessed from System.getProperty("microedition.hostname")"
Anyway, you may have a problem if the phone's IP changes over time. A possible solution to overcome this may be having your J2ME app register its IP regularly so that clients can contact you later, ie some kind of server registry mechanism. [ March 21, 2007: Message edited by: Eduardo Marques ]