C → S {type:'sip_presence_subscribe', to:…, expires:…}

Subscribe to SIP presence information. Server will send sip_presence_notify messages every time requested client's presence status changes.

arguments:

• to - SIP address of client you are interested to know status of
• expires - time in seconds before subscription expires

If you subscribe to your own status (to is set to your own SIP address) you will receive a sip_presence_notify message containing a list of everyone currently subscribing to your status.

S → C {type:'sip_presence_subscribe', from:…, error:'404', msg:'Not found'}

If you attempted to subscribe to an unused SIP address (noone registered) a 404 error is returned.