Modification of sipconf for screen sharing

Introduction

I added screen sharing function to sipconf. This document describes the modification parts of sipconf.

Requirements

• Receive 'INVITE' message including 'vncserver' or 'vncviewer' as a media type in m line;
  m=application 5905 TCP vncserver
  m=application 5505 TCP vncviewer
• In case of a vncserver participant, receive a password included in k line of 'INVITE' message and use it for VNC authentication;
  k=clear:password
• In case of a vncviewer participant, create a random password for VNC authentication and send it to the participant in k line of '200 OK' message. The password is different for each participant.
  k=clear:password
• When there is a vncserver participant and another participant sends "INVITE' message as a vncserver, sipconf rejects the request.
• When there isn't a vncserver participant and a participant sends 'INVITE' message as a vncviewer, sipconf sends back "200 OK" at once and keeps the participant wait until a vncserver participant joins.
• After signaling with a vncserver participant, sipconf does initial handshaking as a vncviewer with the vncserver. After initial handshaking, sipconf receives messages from the vncserver and sends them all the vncviewer participants.
• After signaling with a vncviewer participant, sipconf does initial handshaking as a vncserver with the vncviewer. After initial handshaking, sipconf receives messages from the vncviewer and sends them to the vncserver.

Implementation

I created two threads. One is VNCClientThread and the other is VNCServerThread.

1. VNCClientThread
This thread communicates with a vncserver participant program and works as a vncviewer. This thread is created when a vncserver participant joins a conference. This thread does

• connect to a vncserver
• initial handshaking with the vncserver
• receive messages from the vncserver
• send the messages to all the vncviewers

2. VNCServerThread
This thread communicates with a vncviewer participant program and works as a vncserver. This thread is created when a vncviewer participant joins a conference. This thread does

• accept a connection from a vncviewer
• initial handshaking with the vncviewer
• receive messages from the vncviewer
• send the messages to the vncserver

Modified files

I modified the following files. They are in http://www.cs.columbia.edu/~koguchi/ScreenSharing/src/sipconf/. tar file is here.

1. libmixer/rtpmapi.c, rtpmapi.h
   • add members related to vnc to rtpm_call_leg_t
   • add members related to vnc to rtpm_conf_t
2. libmixer/sdp.c, sdp.h
   • add media_transport_type definition
3. libmixer/video.c, data.c
   • add media_transport_type setting
4. libmixer/module.mk
   • add my added file names
5. libsip++/sipsdp.cpp
   • add k line handling
6. sipconf/main.cpp
   • add Transport Type
   • add parsing password from k line

I added the following files in libmixer directory.

1. libmixer/vnc.c, vnc.h
   • include VNCServerThread and VNCClientThread
2. libmixer/vncinit.c, vncinit.h
   • handle VNC initial handshaking
3. libmixer/vncauth.c, vncauth.h
   • the same as original VNC program
4. libmixer/d3des.c, d3des.h
   • the same as original VNC program
5. libmixer/rfbproto.h
   • the same as original VNC program

Limitations

• When a vncserver participant uses Windows machine and a vncviewer participant also uses Windows machine, the vncviewer participant can't see the vncserver's Windows desktop, althogh vncviewer participants who use Sun or Linux can see the Windows desktop.
• When a vncserver participant hangs up before vncviewers, the vncviewer's screen doesn't close automatically.

Last updated by Kazuumi Koguchi