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Re: UDP Packet Encoding

by ikegami (Pope)
on Nov 21, 2011 at 23:57 UTC ( #939344=note: print w/ replies, xml ) Need Help??

in reply to UDP Packet Encoding

Taking it at your word that documentation cannot be obtained, that leaves reverse engineering the data.

There's not that much to the packet, so most of it can probably be guessed based on what data you expect to be provided.

  • Id? (Serial number?)
  • Timestamp?
  • Longitude?
  • Latitude?
  • Altitude?
  • Speed?
  • etc

Things to know:

  • Learning how integer and decimal numbers are stored by computers (2s complement and floating point) would be useful.

  • Familiarity with different representations of longitude and latitude could be useful.

I was about to say that reverse engineering data is possibly more art than science, but that's not true at all. To reverse engineering data, apply scientific principles:

  1. Create a hypothesis as to the value of a byte or collection of bytes.
  2. Devise an experiment to prove the hypothesis.
  3. Execute the experiment.
  4. Rinse and repeat.

Things to look for:

  • Which numbers change as you move the unit? That could be the coordinates.

  • Are some number ever increasing? Then it's surely a counter, maybe a timestamp.

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