[Kamailio-Users] correct usage of t_reply

[David Aldworth]

I'm am attempting to return a 503 "Service Unavailable" after my  
kamailio server sends the provisional response to customer UA if we  
cannot find a route for the call. I am using:

t_reply("503", "Service Unavailable");

However this results in:

ERROR:tm:w_t_reply: failed to send a t_reply to a message for which no  
transaction-state has been established

Reading up on t_reply, it clearly states: "Sends a stateful reply  
after a transaction has been established." So, I guess thats means  
even though we have received the invite, and send 100 Trying back, a  
transaction does not actually exist.

So, my question is, how do I tell the sending UAC that we are 5XX so  
that it can stop sitting there waiting for session progress?

Thanks for any help.

David