Activities/Classroom Broadcast

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Revision as of 10:09, 28 November 2011 by RafaelOrtiz (talk | contribs)
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ClassroomBroadcast transmits the screen of the 'server' laptop to the screens of a number of 'client' laptops. Typically the teacher's laptop would be the server and the students' laptops the clients. ClassroomBroadcast is a low cost alternative to using a data projector. ClassroomBroadcast runs on the server laptop and a VNC client such as TigerVNC runs on the client laptops.


Install ClassroomBroadcast on the 'server' laptop from

ClassroomBroadcast also requires some additional software - x11vnc

To install x11vnc enter the following in Terminal:

sudo yum install x11vnc

Install a VNC client on all the client laptops, in Terminal enter:

sudo yum install vnc


Check that all laptops are connected to the same network. Start ClassroomBroadcast on the server laptop. Press the button in the centre of the screen and note the IP address, eth0:, below the button.

Screenshot of "ClassRoomBroadcast Activity".png

Start the VNC client on the client laptops by entering the following in Terminal


Enter the IP address eth0: from the server into the dialog box.

Screenshot of "VNC Viewer- Connection Details".png

Alternatively you can specify the IP address in the command and skip the dialog box


Fullscreen mode allows the client to see the full screen but the client cannot quit till transmission stops

The fullscreen mode can be selected in options in the dialog box or specified from the commandline

vncviewer -fullscreen

The screen of the sending laptop is mirrored on the receiving laptops. It takes a few seconds for the screens to update.

To stop transmitting, click the centre screen button in ClassroomBroadcast. ClassroomBroadcast can be closed like any regular Sugar Activity. When you are finished with the clients, you can close them by clicking the X in the screen upper right which returns you to Terminal. Terminal can then be closed like any regular Sugar Activity.

Known issues

With ClassRoomBroadcast V2 and TigerVNC Viewer 1.0.90

  • Can only run one client, attempting to connect a second client gives 'end of stream'

to fix add the option "-shared" at line 194 of

  • Cannot disconnect and restart the client, error 111 connection refused

to fix add the option "-shared" at line 194 of

  • The client gets seemingly random clipboard entries 'type clipping'
  • Stopping the server first works OK, the client then quits. If you quit the client first then you have to click the server stop button twice to stop transmission
  • The server cursor does not appear in the client laptops - fix, uncheck render cursor locally in TigerVNC options