I played around with a couple options and found that issuing a hupall normal_clearing on the initiated call after a few seconds was the most reliable way to do this. The next best option I found was hanging up after a few seconds of receiving CS_EXECUTE state update, though this seemed to cause the timing to vary.

Are there other events that come over ESL on a PRI call that are good to anchor to? For some of the suggestions above like "progressing", it isn't clear what event that corresponds to.

On Thu, May 13, 2010 at 5:14 PM, Neil Patel <neilp@cs.stanford.edu> wrote:
Thanks Michael, I was looking for code examples to receive events over ESL, and found them in libs/esl/.

I'm still not clear on the following:
  1. I have a controller script that originates calls; it runs "show channels" between calls and parses out the number of active channels. If below threshold, originate next call. If not, wait a couple seconds and run "show channels" again, repeating till below threshold. Is this the best way? Can this be done more efficiently through events? How?
  2. For placing missed calls to SIP endpoints, it sounds like I can wait for a signal 180 or 183 to know when to hang up. How do I check for those signals? Is this another job for events?
  3. For placing missed calls over openzap/PRI, it sounds like I can check for call states PROGRESS or ALERTING? Where are those states from, and how do I check them? Again, can I use events? The other option you gave is checking for endpoint_disposition. This is in the cdr, but how do I use it for detecting when I should hang up for a missed call? Is there an event associated with it? What are the call states it goes through?
-Neil

On Wed, May 12, 2010 at 2:47 PM, Michael Collins <msc@freeswitch.org> wrote:

On Wed, May 12, 2010 at 11:59 AM, Neil Patel <neilp@cs.stanford.edu> wrote:
Thanks for the tips.

Where are there examples of using ESL to register and handle events? For e.g. I don't see any example of how to register for a change in channel variable endpoint_disposition. Or even to check the CHANNEL_STATE event.

-Neil

Neil,

Check out the event socket documentation, specifically the "events plain all" and "filter" commands. You can listen to all events or just specific ones:
http://wiki.freeswitch.org/wiki/Event_socket

If you want to experiment with the event socket and the various events then use fs_cli. Connect with fs_cli and then issue "/log 0" which turns off all debug messages. Now you have basically a raw event socket. Try some of these commands:

/event plain all

watch the fun messages fly. :)

You can filter them as well:

/filter Event-Name CHANNEL_STATE
/filter Event-Name CHANNEL_HANGUP

when you apply a filter you will receive only those things you choose. A it's a "filter in" not filter out. Another way of saying it is "show me events named CHANNEL_STATE" and "show me events named CHANNEL_HANGUP"

just note that in your script you will be using the ESL abstractions for these:

http://wiki.freeswitch.org/wiki/Esl#ESLconnection_Object

I hope that helps! Have fun.
-MC

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