Content-Length: 0 Expires: 60 ]]> ;tag=[call_number] To[$3] Call-ID: [call_id] Cseq: 1 NOTIFY Contact: sip:sipp@[local_ip]:[local_port] Max-Forwards: 70 Event: presence Subscription-State: active;expires=50 Content-Type: application/pidf+xml open ]]> Content-Length: 0 ]]>