Experimental Physics and
Industrial Control System

Ralph Lange <[email protected]> · Sat, 19 Dec 2015 18:32:13 +0100

On 19/12/2015 17:24, Johnson, Andrew N. wrote:

Please bear in mind that the code that you posted comes from the CA client, not the CA Repeater, and it's the repeater that sees the UDP packets — C++ clients get their beacons over TCP from the repeater. Inside ca_repeater() there is a statement that copies the beacon source IP address into a field of the beacon message before redistributing it, provided that address was zero in the incoming UDP message. The comments immediately above your code snippet describe this, although they call the repeater something like a fan-out server. I was reading through this yesterday and the code I looked at matched up with the comments, but I didn't check the code that actually generates the beacons.

Correct.

But that copying of the UDP sender address happens only if the message

content was empty (zero), which is the behavior of old servers. New

servers (that how I interpret that comments) do fill in the message

content on the server side, which means that it does not get overwritten

by the repeater or client.

Also, Anze's wireshark data is taken from the network, not the local

socket between client and caRepeater. This makes me pretty sure his

server is new enough to fill in the beacon message contents itself.

The sending code is in rsrv/online_notify.c, lines 240ff.

For each element in the list of beacon addresses to send to, it

connect()s the beacon socket, then calls getsockname() on it and puts

the address it gets inside the beacon message.

  I don't know whether the Java library relies on the repeater so it might do things differently. Presumably Anze is using 3.15.3, could you also check against a 3.14.12 IOC in case the multi-interface changes in 3.15 broke the beacon generation code.

As far as I know, Anze is using a 3.14.12 IOC, and the single-interface

changes in 3.15 do not apply.

Cheers,
~Ralph

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System