Disable function codes

[dlmoffett]

Hey, I've got a funky application where, as a Server, I need to disable many standard function codes, and more importantly, return the IllegalFunction response if a client transmits a request for a disabled function code.

Specifically we are only supporting function codes 3 and 16.

I've searched and cannot find any obvious/easy way of doing this.

[zufar-ik]

❤️

[janiversen]

The simulator datastore can do that. Alternatively you can patch the framer.

[dlmoffett]

I was going down the patch route but it wasn't immediately obvious to me what the framer should do in order to have the device actually send the illegal function response.

• Is there an exception the framer should raise (I was having a hard time determining where any such exception gets caught and how it gets handled)?
• Or should it mangle request - replacing the function code with an obviously invalid one?
• Some other, more intelligent option?

[janiversen]

Well look at the code, that's about the best advice I can give you...the framer can reject a frame, manipulate a frame and/or generate responses, but of course you need to dig into the code to understand how it works.