I don't know if this addresses what you've asked, but let me add the difference between specifying a port and not is relevant.
If you do not state the port then you are addressing a remote phone's SMS/MMS inbox but MIDlets on the remote side won't have access to it at least through the WMA API.
When a port is part of the address , it may be read by MIDlets using WMA in the remote phone. Note also that some ports may be reserved or blocked. [ April 01, 2007: Message edited by: Eduardo Marques ]