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stlehmann / pyads

Python wrapper for TwinCAT ADS
MIT License
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Read Frame Error due to NetBIOS #77

Closed Adrian-at-CrimsonAzure closed 5 years ago

Adrian-at-CrimsonAzure commented 5 years ago

When I make a connection to a specific PLC (don't know the model offhand) it queries my computer's NetBIOS name directly. Ubuntu denies this request, and then the PLC loops through its saved hostnames broadcasting and waiting for an answer which my PC eventually responds to. Trouble is, even when I set the timeout to 30 seconds it still "times out".

2019-07-15T08:58:51-0400 Info: Connected to 192.168.200.210
2019-07-15T08:59:02-0400 Error: read frame failed with error: 104
2019-07-15T08:59:02-0400 Info: connection closed by remote

That read error happens when the PLC sends a TCP message to my computer acknowledging its existence and pyads (or the underlying ADS library) closes the connection. image

Is there a way to make Ubuntu respond to these direct NetBIOS requests? If not, then is there a way to prevent the connection from closing when there is a read frame error?

Adrian-at-CrimsonAzure commented 5 years ago

This didn't solve the issue, but it was the cause of the issues I was having on my Ubuntu Server install. NetBIOS support is needed on Linux distributions, this is included in most desktop distros but it's not a given on server distros. For example, Ubuntu Server needs avahi-daemon in order to correctly read tags from a PLC.

kryskool commented 5 years ago

@Adrian-at-CrimsonAuzre

Can you test tips found here

edit your /etc/nsswitch.conf file search for the line starting with hosts (my line was like this "hosts: files dns") add wins at the end of the line ("hosts: files dns wins")

It can be necessary to install winbinds

apt-get install winbinds

regards,

Adrian-at-CrimsonAzure commented 5 years ago

Still doesn't work. I can ping my hostname from Windows just fine and I can ping Windows computers in Ubuntu, but my Ubuntu PC actively refuses the connection when sent a blank query. This PLC is running the oldest version of TwinCAT out of all our Beckhoffs, maybe updating it would help?

Adrian-at-CrimsonAzure commented 5 years ago

Moved my project from an Ubuntu Server development VM to the production CentOS VM and all is well? I'm pretty sure Samba on the CentOS VM is the only difference between the two environments. I'm going to chalk it up to that and close this.