Experimental Physics and
Industrial Control System

Jörn Dreyer via Tech-talk <tech-talk at aps.anl.gov> · Tue, 17 Oct 2023 16:06:29 +0200

Hello

Sorry for not citing the old messages. I just found the topic on tech-talk as I was looking for a strange behavior I observed when playing around with NDPluginPVA.
I was able to do a "pvget some_pv" on the machine where the IOC is running, but not on another machine. I had exactly the same ideas as commented here (adding ports 5075/5076 to the firewall) but without luck.
Then I started up wireshark and tested with and without firewall and figured out whats going on.

Without firewall:

Clients sends from port XXX to 5076
Server replies from port YYY to XXX
Client can read data!

With firewall:

Clients sends from port XXX to 5076
Server replies from port YYY to XXX
Client replies with ICMP message
Server gives up, no data transfered!

Of course port XXX is not covered by the firewall rules and is random (> 50000 in my case). One can get around this if you open your firewall for all UDP traffic.
But that is not what you really want to do in a bigger network with lots of broadcast traffic. So opening ports 5075/5076 is not necessary.

So my hope is that one can force pvget/pvput to use a dedicated port that can be added to the firewall rules.

Regards,

Jörn

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System