Hi, many phones as Thomson S2030 or Grandstream 3000 allow presence BLF. Unfortunatelly I think BLF (Busy Lamp Field) just works with Asterisk and it's not a RFC or a draft.
Thomson S2030 allow subscribing to a extension state and it generates this SUBSCRIBE:
------------------------------------------------------------------------------- SUBSCRIBE sip:211@domain.org:5061;user=phone SIP/2.0 Via: SIP/2.0/UDP 192.168.1.97:5061;branch=z9hG4bK4293581925314869375 From: sip:210@domain.org:5050;tag=c0a80101-167c2d To: sip:211@domain.org:5061 Call-ID: 8b5c839-c0a80101-d-d5@192.168.1.97 CSeq: 1 SUBSCRIBE Max-Forwards: 70 Event: dialog Accept: application/dialog-info+xml Expires: 3600 Contact: sip:210@192.168.1.97:5061;user=phone User-Agent: THOMSON ST2030 hw5 fw1.52 00-14-7F-00-68-81 Content-Length: 0 -------------------------------------------------------------------------------
Is there any possibility to use this BLF feature with OpenSer in any way?