packet sniffing?

Hi, I know a bit about using matlab for analysis, however ... I have an RFID (radio frequency identification tag) reader that is sending information over a network to a data logger. Am I able to use matlab to 'listen in on the conversation' for certain information, and when the right bits of info occur, have matlab automatically control a camera to take a picture? thanks for any help. cheers, Clint

Answer 1

[Sean de Wolski]

Yes, that should be doable. Use a timer function to periodically read in the data and analyze it. When the results meet what you're looking for have it control a camera. Image Acquisition Toolbox would probably be your friend.

Answer 2

[Walter Roberson]

Sniffing would not necessarily be impossible, but unless the reader is deliberately sending broadcast or multicast packets, you would need to use uncommon equipment to make it work.

There was a time when the equipment was very common, a time when you practically could not avoid sharing multiple conversations on the same wire, but as network technologies moved on, the more efficient equipment that replaced the former equipment only sends packets where they need to go, and the market for the older equipment dried up.

It can, without question, be made to work if you have the right equipment configured the right way. Any competent network administrator, given an equipment budget (and authorization), could set it up. I have set up such things myself more than once.

Once the relevant packets are making it as far as the machine that will do the sniffing, software on that machine needs to request the sniffing. As sniffing is a security risk and as it slows down network operations, operating systems usually require elevated privileges to turn on sniffing.

I would tend to doubt that the TCP/UDP/IP facilities in the Instrument Control Toolbox would be suitable for sniffing. The MATLAB File Exchange contribution tcpudpip I know to be based upon underlying libraries that are able to sniff (with authorization.) I have never looked to see whether those capabilities are exposed to the MATLAB layer; what I can say is that that contribution could (at worst) be extended to support sniffing by adding a relatively small amount of mex code.