Added RFC3842 - Message Waiting functionality

[mitre-mgarber]

This PR adds support for RFC3842, which allows for a client to send a SUBSCRIBE message to a server in order to be sent NOTIFY messages when someone has left a message for a user, which the server will do for the period specified.

This is a requirement for Video Relay Services Interoperability, which is primarily aimed at supporting the deaf/blind community - though it should be applicable outside of this context as well.

We did this with a very basic subscribe module, which is not as detailed as PR 711 - if it's preferred, I could talk to that author about incorporating some of the specifics in there.

[ikq]

Hi !

I noticed that you mentioned my PR 711, so I checked how it can be used for RFC 3842.
Seems without changes, you just have to develop a parser for the NOTIFY body.

I tried to modify my test:
https://github.com/ikq/subscribe_notify_test

to send SUBSCRIBE according RFC3842

SUBSCRIBE sip:alice@vmail.example.com SIP/2.0
      To: <sip:alice@example.com>;tag=4442
      From: <sip:alice@example.com>;tag=78923
      Date: Mon, 10 Jul 2000 15:55:06 GMT
      Call-Id: 1349882@alice-phone.example.com
      CSeq: 8 SUBSCRIBE
      Contact: <sip:alice@alice-phone.example.com>
      Event: message-summary
      Expires: 86400
      Accept: application/simple-message-summary
      Content-Length: 0

Result:

   SUBSCRIBE sip:user3@example.com SIP/2.0
  Via: SIP/2.0/WSS qngoceuqd83q.invalid;branch=z9hG4bK4170069  
  Max-Forwards: 69
  To: <sip:user3@example.com>
  From: "user2" <sip:user2@example.com>;tag=g7ac7k0a9r
  Call-ID: ql9cn510ur3dlh4sarqb
  CSeq: 3675 SUBSCRIBE
  Event: message-summary
  Expires: 86400
  Accept: application/simple-message-summary
  Contact: <sip:user2@v19oh3q8o209.invalid;transport=ws>;+sip.instance=" 
 <urn:uuid:c51e38d8-ff7f-475b-bec7-db6158392d6f>"
  Allow: INVITE,ACK,CANCEL,BYE,UPDATE,MESSAGE,OPTIONS,REFER,INFO,NOTIFY,SUBSCRIBE
  Supported: outbound
  User-Agent: JsSIP 3.8.0
  Content-Length: 0

Note: user names and domain was changed to user??? and example.com

Code:

    let user = 'user3';
    let eventName = 'message-summary';
    let expires = 86400;
    let accept = 'application/simple-message-summary';
    let target = user; 
    let params = null;

    try {
        subscriber = jssipUA.subscribe(
            target,
            eventName,
            accept, {
            expires,
            params
        });
    } catch (e) {
        console.log('Error: cannot create subscriber', e);
    }

  subscriber.on('notify', (isFinal, notify, body, contentType) => {
     /* Please parse notify body, e.g.
 
         Messages-Waiting: yes
         Message-Account: sip:alice@vmail.example.com
         Voice-Message: 4/8 (1/2)
    */
    console.log(body);         
  });

[ibc]

I don't see anything related to dialogs generated by the SUBSCRIBE request. I mean: a SUBSCRIBE generates a dialog so NOTIFY messages received from the remote endpoint should match such a dialog (there could be many subscription dialogs active at the same time). Do I miss something?

@jmillan your thoughts?

[jmillan]

As @ikq, indicates, once his PR is accepted the addition for SUBSCRIBE packages will be doable, externally if not inside JsSIP. But this PR does not comply with dialog usage as @ibc says and other considerations.

I'm closing this PR.