urgent alarm identification

[sbaik]

running a system on Mango 3.0. Everything is working fine, but have gotten this urgent alarm that returns to normal after a few seconds.

Exception from modbus master: Bad file descriptor (ioctl FIONREAD failed)

Would like to know how to locate the problem causing the alarm. It happened about 7 times in Feb and 3 so far in Mar. It came to my attention after I started alarms to be sent out via text recently.

Thanks in advance

[phildunlap]

Hi sbaik, welcome to the forum!

I am guessing this is Modbus serial? I can't say I've seen that many times, i would wonder things like,

1. Does the serial port get momentarily disconnected? I think you would see it reconnect in the dmesg output.
2. Could someone be issuing different baud reads (perhaps through the API or modbus tools) to this serial line?
3. Do you miss data for a while when this happens?

[sbaik]

Hi phildunlap,

It looks like the problem is gone after increasing the update period and the timeout. It must have been timing out momentarily.

Thanks for your suggestion.

[phildunlap]

Thanks for sharing the resolution!

[sbaik]

@phildunlap Unfortunately, got the error again. I don't think it had anything to do with the solution I posted above; just a coincidence it stopped for a while. It returns back to normal in a few seconds ,shorter than our refresh time, so it isn't losing any data. It is modbus TCP. It must be just dropping signal. It is at a rural location. I just figured losing connection would alarm a different message.

[phildunlap]

That makes more sense than it being a timeout. A timeout would have produced a ModbusTransportException with timeout as its message, not an operating system message about a file descriptor having issues.