[asterisk-users] SIP MESSAGE outside calls - state of the art?

[Roger Burton West]

I have a mobile phone (UTStarCom GF-210) that uses SIP MESSAGE to send
"SMS" messages over VoIP. My Asterisk 1.4 installation drops these
messages and returns a failure condition to the phone:

[Feb  9 10:17:22] WARNING[11960]: chan_sip.c:9859 receive_message: Received message to <sip:2542 at firedrake.org> from "Display Name" <sip:mob776 at firedrake.org>;tag=87739132, dropped it...
  Content-Type:text/plain; charset=UTF-8
  Message: test message

(Packet trace shows a SIP MESSAGE, answered by a 405.)

...and apparently is unable to originate them either; SendText, which
looks as though it ought to be the right way to send them, produces (in
the context of a call, since I can't send the message outside one):

    -- Executing [604 at default:2] SendText("SIP/mob776-02ba6050", "test message") in new stack
    -- Incoming call: Got SIP response 405 "Method Not Allowed" back from 10.0.155.21

even though it's also making a SIP MESSAGE request.

The only documentation I can find talks about a patch and is pretty old:
http://www.voip-info.org/wiki/view/Asterisk+SIP+Messaging

What I would like is to be able to send a textual message from the phone
into an AGI script (or for other processing), and to return results the
same way. Is anyone doing this with later versions of Asterisk, or
indeed anything else?

Roger