MulticastVNC
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DISCONTINUED - but take a look at the TeleTeachingTool
Transmitting and Recording Desktop, Audio and Video
http://TeleTeaching.Uni-Trier.de

MulticastVNC with Recording/Playback Feature

MulticastVNC adds multicast funcionality to VNC for the purpose of teleteaching. In a teleteaching environment the teacher is the only one to do changes to the desktop. But the desktop should be visible to all students. With standard (unicast) VNC you need to transfer all data to each student resulting in huge network traffic. Multicast is a typical solution for this one-to-many environment. I changed the original Java vncviewer so that it provides the functionality of a (standard) VNC viewer, a multicast VNC viewer and a multicast VNC server. It is plattform independent because it's done in Java.

TeleTeachingTool - software and informationen about an extension of MulticastVNC incuding audio and video.

Usage

java vncviewer HOST host PORT port [MULTICAST maddress[:mport[/ttl]]] [PROXYPORT pport] [FILE file]
java vncviewer FILE file

If you don't know how to a start a VNC server read VNC documentation.

VNC Viewer

Starting a vnc viewer that connects to the vnc server "dumpf:5901".
java vncviewer HOST dumpf PORT 5901
If a multicast vnc server is found it runs as multicast client.

VNC Multicast Server/Proxy

Starting a standard vnc viewer with multicast server functionality. Works as a proxy between unicast and multicast world.
java vncviewer HOST dumpf PORT 5901 MULTICAST 230.0.0.1:3333/16 PROXYPORT 6666
"dumpf:5901" specifies the (standard) vnc server.
The multicast vnc server will be available at "dumpf:6666".
The multicast group "230.0.0.1" with port "3333" is used to send multicast messages.
"16" specifies the Time-To-Life of each packet.

So this works as a proxy between unicast and multicast vnc.

java vncviewer HOST dumpf PORT 6666
connects to the multicast vnc server started with the command before.

Recording a session

You need to specify HOST,PORT,MULTICAST parameters as mentioned in above. Add a FILE parameter to specify the output file. 
java vncviewer HOST dumpf PORT 5901 MULTICAST 230.0.0.1 FILE dumpf.vnc
NOTE: You have to send multicast messages to record.
NOTE: Format of Recording

Playback

You only need to specify the FILE parameter. 
java vncviewer FILE dumpf.vnc
Some new buttons will appear in the top row of the viewer window. They deliever some standard features like play,pause,stop,fast forward(with different speeds) and step forward/step back.

NOTE: The displayed time is the timestamp of the last message and not the real playback time. So if there are no changes for a while the player seems to be sleeping, but it is just the incorrect timer.

Download

NOTE: This is still an early public release.But it should work and it's for free.

MulticastVNC_0.2.zip
  • added: record/playback
  • added: connecting clients in threads (bad client can't block others anymore)

MulticastVNC_0.1.zip
  • first public release

Troubleshooting

  • Multicast is not working:
    • using Linux: Check if multicast support is enabled in Kernel (if not, multicast join is not reliable)
    • Is the time-to-live used for sending multicast pakets correctly set.
        TTL value    Range
        0 Local host
        1 Local network (subnet) [DEFAULT]
        32 Site
        64 Region
        128 Continent
        255 World
    • Check if your network allows multicast. Ask your administrator. If a router doesn't allow multicast you're lost.
    • Are you using a multicast address ? (224.0.0.0 - 239.255.255.255)
  • VNC server related:
    • Does the VNC server disconnects your client ? Try starting with options -dontdisconnect -alwaysshared. (see VNC documentation)
    • Setting display size of VNC server, window manager and more - see VNC documentation.