snmp raw device

[Torsten Juergens]

A long time ago I activated the Cinelister Control Interface on the Doremi and have been using it ever since to control the projector, volume, lights etc.
Now I thought why not the UPS which unfortunately wants to communicate via snmp. But easier said than done.

Well, is it possible to send a snmp set command as text string to a UPS via a raw device from the Doremi DCP?
The matching UPS-MIB is available.
And I have successfully tested the UPS with SnmpB.

[Leo Enticknap]

As long as it can send strings on UDP port 161, I see no reason why you couldn't send SetRequests that way, meaning that you could send one way commands. The problem is that, AFAIK, the Doremi has now way of reading and acting on responses or traps received, unless there is a way to turn these into trigger cues, which I'm not aware of.

[Torsten Juergens]

Thanks Leo, I just want to send "shutdown" and "startup" to UPS anyway. I'll try that out tomorrow.

[Harold Hallikainen]

When I wrote SNMP stuff for the JSD series, I THINK it was UDP (but I don't really remember). I think the S for Simple in SNMP is not accurate. I had a hard time getting it to work. Anyway, doesn't the Doremi raw device do TCP instead of UDP? Maybe it will do both, and maybe you can do SNMP on TCP...

Harold

[Steve Guttag]

Yeah, there is nothing "simple" in SNMP

[Torsten Juergens]

The device has successfully contacted the UPS on UDP port 161.
Now "only" the syntax has to be correct.
Let's see how long that takes.

[Marcel Birgelen]

SNMP is a binary protocol, and your SNMP-set command must include at least the following parameters:
- The SNMP version you're using, afaik part of the header.
- The type of command you're doing: a SET in this case.
- The community string if you're using v1 or v2 of the protocol. Try to avoid v3 in this case.
- The OID you want to set, which has to be in numerical form.
- The value you want to set.
- Some checksum information to check if the packet survived transport.

This isn't something you simply formulate yourself, so what you could do is use a tool like this.

It's a python script that allows you to perform an SNMP set command. You can tweak it until it works and then you can output the raw packet in HEX format with the "-d" option. That output should be usable to construct the binary string that your Doremi server needs to send.

[Torsten Juergens]

Thanks Marcel,
We'll see what my learning curve looks like.
Unfortunately, I'm only on site every few weeks.
So it will take a little while.