Applications

Supported Media

The INVITE and subsequent re-INVITE methods may contain one or more media types supported by the server. Each conference room mixed audio, instant messages and uploded files are dispatched to all participants.

Audio

The INVITE must propose a session with RTP (m=audio in SDP). Re-INVITE to add or remove audio to existing session is supported. Opus, G722, wideband speex and G711 codecs are supported. For encryption, sRTP and ZRTP key exchanges are supported.

Content-Type: application/sdp
Content-Length: 233

v=0
o=- 3526098545 3526098547 IN IP4 81.23.228.139
s=Sylk Server-1.2.3
t=0 0
c=IN IP4 81.23.228.139
m=audio 55324 RTP/AVP 9 101
c=IN IP4 85.17.186.7
a=rtcp:55325
a=rtpmap:9 G722/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=crypto:1 AES_CM_128_HMAC_SHA1_80 inline:1nDEh/WrJ57RBaHwhBG4+RAwzV9k/HxZhg1wClnx
a=sendrecv

Instant Messaging

The INVITE must propose a session with MSRP chat over TLS (m=message and a=path:msrps in the SDP). Re-INVITE to add or remove chat to existing session is supported. Private messaging extension between participants is also supported.

Content-Type: application/sdp
Content-Length: 213

v=0
o=- 3526098545 3526098547 IN IP4 81.23.228.139
s=Sylk Server-1.2.3
t=0 0
m=message 60167 TCP/TLS/MSRP *
c=IN IP4 81.23.228.139
a=path:msrps://81.23.228.139:60167/f8d1058769bebacacf62;tcp
a=accept-types:message/cpim
a=accept-wrapped-types:*
a=setup:passive
a=chatroom:private-messages

File Transfer

The INVITE must propose a session with MSRP file transfer media description. Re-INVITE to add a file to existing session is supported. Participants that join later can request the previously uploaded files by using MSRP pull method.

Content-Type: application/sdp
Content-Length:   407

v=0
o=- 3526099467 3526099468 IN IP4 81.23.228.139
s=Sylk Server-1.2.3
c=IN IP4 81.23.228.139
t=0 0
m=message 39084 TCP/TLS/MSRP *
a=path:msrps://81.23.228.139:39084/a06af01b810519fb6090;tcp
a=recvonly
a=accept-types:*
a=accept-wrapped-types:*
a=setup:passive
a=file-selector:name:"Blink.pdf" type:application/pdf size:151036 hash:sha1:49:AD:49:...

Screen Sharing

This functionality is implemented as com.ag-projects.screen-sharing extension to the chatroom functionality.

Content-Type: application/sdp
...

m=message 40278 TCP/TLS/MSRP *
a=path:msrps://81.23.228.149:40278/2aa5bbb5d37731ef85c0;tcp
a=accept-types:message/cpim
a=accept-wrapped-types:*
a=setup:passive
a=chatroom:private-messages com.ag-projects.screen-sharing

If the end-point detects and supports this private extension, it can share the screen by pushing at regular intervals a jpeg image with the desktop content over the MSRP chat stream. The image must be encapsulated in a CPIM envelope using content type application/blink-screensharing. Blink SIP client implements this extension.

MSRP eea58af6af1b788 SEND
To-Path: msrps://81.23.228.149:41652/a65812de6f6a0725ee1a;tcp
From-Path: msrps://192.168.1.6:2855/e7028b404511ed77d6a2;tcp
Message-ID: 641f9960ded0638d
Byte-Range: 1-*/245347
Success-Report: yes
Failure-Report: yes
Content-Type: message/cpim

From: Adrian Georgescu <sip:31208005169@ag-projects.com>
To: <sip:nnauyj@conference.sip2sip.info>
DateTime: 2011-12-22T09:12:04+01:00

MIME-Version: 1.0
Content-Type: application/blink-screensharing
ÿØÿàJFIF .............

The server then makes the screenshot available at a HTTP URL and publishes this URL to all participants using the conference information notification using <agp-conf:screen_image_url> extension. Participants can see the screen using a specialized client or a regular web browser.

Conference Information

To obtain the conference information send a SUBSCRIBE request to the room URI for Event conference RFC 4575. The NOTIFY contains detailed information with the list of participants, their connected endpoints, media type and stream status and information about uploaded files.

Content-Type: application/conference-info+xml
Content-Length:   975

<?xml version='1.0' encoding='UTF-8'?>
<conference-info xmlns:agp-conf="urn:ag-projects:xml:ns:conference-info"
    xmlns="urn:ietf:params:xml:ns:conference-info"
    entity="sip:agp@conference.sip2sip.info" state="full">
    <conference-description>
        <display-text>Ad-hoc conference</display-text>
        <free-text>Hosted by Sylk Server-1.2.3</free-text>
        <agp-conf:resources>
            <agp-conf:files>
                <agp-conf:file name="Blink.pdf" hash="sha1:49:AD:49:...."
                size="151036" sender="AG <sip:31208005169@ag-projects.com>" status="OK"/>
            </agp-conf:files>
        </agp-conf:resources>
    </conference-description>
    <host-info>
        <web-page>http://sylkserver.com</web-page>
    </host-info>
    <conference-state>
        <user-count>1</user-count>
        <active>true</active>
    </conference-state>
    <users state="full">
        <user entity="sip:31208005169@ag-projects.com" state="full">
            <display-text>Adrian Georgescu</display-text>
            <agp-conf:screen_image_url>https://81.23.228.146/?image=WfPeNYF195.jpg</agp-conf:screen_image_url>
            <endpoint entity="sip:pbvusniw@95.97.50.27:54325" state="full">
                <display-text>Adrian Georgescu</display-text>
                <status>connected</status>
                    <joining-info>
                        <when>2011-09-27T09:49:05+02:00</when>
                    </joining-info>
                <media id="170092876"><type>message</type></media>
                <media id="2977223756"><type>audio</type></media>
            </endpoint>
        </user>
    </users>
</conference-info>

Participant Management

To add and remove participants, Sylk Server supports INVITE and REFER methods as defined in RFC4579 (Conferencing for User Agents). One can remove or add participants by sending a REFER method to the conference URI.

REFER sip:agp@conference.sip2sip.info SIP/2.0
Via: SIP/2.0/UDP 10.211.55.2:54325;rport;branch=z9hG4bKPj7PFxy8RLtr20jfVyUx2eis1H7.1aY7Np
Max-Forwards: 70
From: "Adrian Georgescu" <sip:31208005169@ag-projects.com>;tag=ZtGlJFOgGvwWQEMae6uTpuhT1aREkQeR
To: <sip:agp@conference.sip2sip.info>
Contact: <sip:pbvusniw@192.168.1.6:54325>
Call-ID: rYp1GQbSQ8kFrC1xccpfA5t9GXaR5qwt
CSeq: 6839 REFER
Event: refer
Accept: message/sipfrag;version=2.0
Allow-Events: conference, message-summary, presence, presence.winfo, xcap-diff, refer
Refer-To: <3333@sip2sip.info>;method=INVITE
Referred-By: sip:31208005169@ag-projects.com
User-Agent: Blink Pro 1.3.1 (MacOSX)
Content-Length:  0