[SIPForum-discussion] How does x-lite send a dialed number to asterisk?

Joel Gerber Joel.Gerber at corp.eastlink.ca
Thu May 28 18:47:37 UTC 2015


In answer to your first question, yes, generally a REGISTER message is used to let your SIP server know where you are and what port your SIP application is listening on. This allows your SIP server to direct new calls to you. It is also (sometimes) used as a security mechanism, disallowing you to make any outbound calls unless you have previously REGISTERed.

In answer to your second question, there are 2 circumstances with separate mechanisms that are used to deliver entered digits from one SIP user-agent to another.

Circumstance 1 - Digits are dialed in order to initially reach the remote device. We'll call these the call routing digits. Depending upon your device's programming/configuration, these digits may not necessarily include all of the digits required to reach the remote party, but are at least enough to get you in the right direction. In this case, the dialed digits will be present in the Request-URI of an INVITE message sent from the originating client to his next hop SIP server.

IE: INVITE sip:18001234567 at domain.com;user=phone SIP/2.0

Circumstance 2 - Digits are dialed after the call has already been established. In this case there are a variety of ways to transmit the dialed digits. One way is by using a SIP INFO message with the digits encapsulated within. Another way is by using the telephony-event RTP payload type. And yet another way is by sending them as straight voice.

By the description you've given, circumstance 1 is in effect. The dialed digits are transmitted in the Request-URI of an INVITE message. This is received by Asterisk, who performs a dial plan match to identify the extension in its dial plan to execute. I'm not an Asterisk dial plan guru, so I can't tell you the details of what it can do, but I would be highly surprised if it couldn't execute a shell script on the PBX server.

Joel Gerber
Network Operations Specialist - Telephone
Joel.Gerber at corp.eastlink.ca    T: 519.786.1241

-----Original Message-----
From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Rodrigo Pimenta Carvalho
Sent: May-27-15 4:50 PM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] How does x-lite send a dialed number to asterisk?


I'm new on Asterisk, SIP and softphones.

How does the X-Lite softphone send a dialed number to asterisk? Maybe this question is too generic, so let me clarify a bit more:

1) My X-Lite is already registered on my Asterisk. Was it possible by means of a SIP Register message, wasn't it?

2) If I dial the number 200 in my X-Lite, my Asterisk will execute some actions, because there is the extension 200 in its dial plan. But, to send 200 to Asterisk, does the X-Lite use just a SIP INFO message or does it use SIP INVITE and then SIP INFO? 

Can a Dial Plan execution invokes a shell script on Linux?

Any hint will be very helpful!

Best Regards.

Inatel Competence Center
Ph: +55 35 3471 9200 RAMAL 979
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