Getting UDPTL(SIP):Transmission error:Resource temporarily


I configured Asterisk 10 for inbound fax, for couple of weeks I didn’t see any issues until today. The setup I configured for inbound fax is quite simple i.e. Cisco Voice GW sends the fax calls to Asterisk using T.38 protocol and later Asterisk stores/forwards the fax to specific end user.

The configuration I made in sip.conf for enabling T38 is listed below;

t38pt_udptl = yes,fec,maxdatagram=400
faxdetect = t38

And in udptl.conf, I just uncommented ‘use_even_ports = yes
;’ and rest of it set as default.

Here is the error I’m usually seeing in Asterisk side;

[Jan 15 14:13:28] NOTICE[20514] udptl.c: UDPTL (SIP/ Transmission error to Resource temporarily unavailable

If this notice comes, it occurs repeatedly unless I need to restart the asterisk service. For some reason it also effecingt the V-GW. There is no issue found in the V-GW side.

Please advise what is the reason that I’m getting this message and how can I avoid it?

Forgot to add one more thing, the version of Asterisk I 'm using is 10.4.2

A sendto system call returned EAGAIN. It happens when a write to a non-blocking socket would have blocked if the socket were blocking. That would suggest that you had run out transmit buffers, possibly because the outgoing interface is down.

There are two possibilities here: either udptl.c expects not to write fast enough that the socket will ever block, but wants to fail without stalling, if it does; or someone forgot to treat EAGAIN specially.

That question probably needs taking the developer mailing list or IRC channel. The first case would be intended behaviour, but the second would be a bug.