MODBUS TCP gurus

cjh

Member
Join Date
Mar 2003
Location
Cumming, GA
Posts
235
Question about MODBUS TCP gateways:

If you send a unit identifier value of 0 to a MODBUS TCP gateway, should you wait for a reply?

The spec. is kind of confusing here to me. I know that in a serial MODBUS RTU network, you don't wait for a reply when you do a broadcast but the MODBUS TCP spec. says that a unit identifier of 0 is valid either when you are sending a message to a gateway or to a standard MODBUS TCP server device.

It probably seems trivial but the throughput will definitely be affected if I wait for a reply and no reply is forthcoming (have to wait the entire timeout period). I know that I can buy a gateway to find this out but I was hoping someone here might know the answer and save me a few bucks...
 
Ok...no luck with that question...

<So much for saving a few bucks...>

How about this? For you guys that use MODBUS TCP gateways, what brand and model do you use? And if you know the price as well, that would be great.

Thanks.
 

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