One of the features of the Access Grid which takes it well beyond videoconferencing on steroids is
its ability to share applications. The AG's shared application
mechanism passes events and data, as required by a particular
application, between all the participants in the shared application.
This same mechanism can be used to distribute arbitrary data to shared
application participants. A common example of this is the VenueVNC; the VenueVNCServer
creates a VenueVNC shared application and stores various connection
details. When clients join the shared application session, the stored
connection details are retrieved and used to launch a vncviewer application.
In this example of remote sensor monitoring, the AG's
shared
application mechanism is used to distribute live sensor data to the
shared application participants. The sensor data consists of
temperature outputs from four thermocouples attached to a Weeder Technologies WTTCI-M
thermocouple input module, which is connected to a computer via its
RS-232 port.
The software on the machine hosting the WTTCI-M board consists of two
parts:
- a python module, Weeder.py,
to communicate with the WTTCI-M board via the machine's RS-232 port
- a python program, VenueThermoServer.py,
which
- creates a shared application in an AG venue (nominated as a
startup option)
- periodically retrieves temperature data from the WTTCI-M board
and makes the data available to any participant in the shared
application session.
The
temperature data is now accessible by joining the shared
application session in the nominated venue. Note that entry to a venue
may be restricted (by Globus or SSL certificates for AG2 and AG3
respectively), providing a secure means of making the sensor or
instrument data available to a restricted audience.
To join the shared application session as a "client", the VenueThermoClient
shared application must first be installed. The shared application is
then joined by either double-clicking the session's entry in the VenueClient's
"Application Sessions" section, or right-clicking on it and selecting
"Open" from the resulting drop down menu. The name of the session is
set when the VenueThermoServer is started; if no name is given as a
startup parameter, the default name "Remote THERMO" will be used.
A few seconds later, all being well, the VenueThermoClient interface should
appear.
The VenueThermoClient
interface consists of a display of the temperature data from each of
the four thermocouples attached to the Weeder WTTCI-M board. In the
instance shown here, the window frame identifies the thermocouple data
as being generated at a machine named seivers.vislab.uq.edu.au. The
user is able to select a display of the data in either Celsius or
Fahrenheit units. In the status bar at the bottom of the window frame,
the thermocouple types are shown on the left. On the right of the
status bar, the date and time of the last received data is shown.
Of course we are only monitoring trivial data in this project. However
the general methodology used here could apply to almost any instrument
or sensor data imaginable. Combined with the AG's video and audio
streams, we have a powerful platform for remote instrument and sensor
monitoring.
Downloads
Downloads
are available from the project main site (UQVislab)