[Serusers] SIP client and serweb

[Jiri Kuthan]

At 08:00 PM 1/17/2004, Arnd Vehling wrote:
>Hi,
>
>Daniel-Constantin Mierla wrote:
>> 
>> SER does not manage buddy lists or so. This is not related to session
>> initiation protocol and I am not aware of any SIP client supporting such
>> extension.
>
>Just curious:
>
>Is there any way to find out (using SIP protocol) if a certain SIP-Contact
>is registered (at a specified server?) _without_ sending an INVITE to the
>sip contact?

that's what the asynchronous-based SUBSCRIBE-NOTIFY presence is good for.]
not many UAs implement it though, so you may instead try polling the UAs.
OPTIONS would be a better choice than INVITE since it does not cause the
other party to ring. Nevertheless, you are not really sure who responds
to the OPTIONS -- it may be voicemail too.

-jiri