Re: Post numbers used by CA client

[Ralph Lange <ralph.lange@gmx.de>]

Hi Steve,

A CA client uses ephemeral ports as originating port numbers, correct. 
Ephemeral port numbers are indeed random, and cannot be predicted reliably.

However, if your container contains an IOC (CA server), opening ports 
5064&5065 (in the default setup) for both TCP and UDP should allow any 
client outside the container to connect. (Not much different to a 
container with a web service published at port 80.)
The CA client in the container would still use ephemeral port numbers 
for outgoing connections - do you need to publish those?

Cheers,
~Ralph


On 04/07/2016 16:43, Stephen Molloy wrote:
> I’m trying to build a Docker container for quick set-up and tear-down 
> of EPICS instances, and I’ve run into a problem.  A CA client outside 
> the container, but on the same host, cannot see any PV’s served from 
> inside the container.
> Looking at the network traffic with Wireshark, I can see that the 
> server uses ports 5064 & 5065 as expected, but the ports used by the 
> client seem to be relatively random.  If I could predict them, or 
> (even better) force them to be specific ports, then I could expose 
> those ports in the Docker container and (hopefully) the client and 
> server could communicate properly.
>
> Or perhaps this isn’t the problem, and there is some other network 
> issue getting in my way.
> (I’ve successfully run several EPICS installations on this network and 
> from this computer, so I am confident that this is an issue with the 
> Docker set-up.)
>
> Hopefully I’m on the right track with my thinking, and hopefully 
> someone can let me know how to proceed from here?
>
> In case you’re interested, I’m documenting my work on my blog — 
> http://www.smolloy.com/2016/07/easy-epics-implementation-with-docker/
>
> Thanks (again) for your time,
>
> Steve