Modbus Poll Duration using Server Home IP

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Hello,

I have a question around Modbus communications, specifically the poll duration. While working on items in our test environment we enable a Modbus data source with the server’s home IP (127.0.0.1) and port of 502. The server has no Modbus device attached it to and no simulator or anything listening to port 502.

As expected, the Slave Monitor is 0 since there is no Modbus device for Mango to talk to.

What we get that is somewhat unexpected is successful polls. In the Runtime Status tab, the polls are succeeding, taking about 3.2 seconds each.

We thought we’d see timeouts instead of successful polls. Are there any ideas why the polls aren’t timing out? Is the server sending TCP/IP info back to Mango, and that is triggering the successful poll?

I did turn on I/O logging for the data source, but nothing gets logged outside of the data source being enabled and disabled.

Thanks,
Chad

@cmusselm

If I understood your question correctly:

The "host" is refer to the Modbus Targeted Device IP, which who is hosting the data source not Mango itself.

@cmusselm that is not a list of successful polls it is a list of the latest polls that completed either successfully or with a timeout. An aborted poll happens when the duration of the current poll is longer than the poll interval. in other words, mango is still busy with the current poll when the next poll should happen so it aborts it and reschedules it.

Thanks, Craig, that explains some of the results I've seen.

For the specific example I showed, the poll had a timeout of 4 seconds, and it was coming back in 3.2 seconds. Since there was no Modbus device actually connected to that IP, did Mango report the poll simply because it received TCP/IP info from the server?