Experimental Physics and
Industrial Control System

"Jeff Hill" <[email protected]> · Thu, 11 Jun 2009 18:26:00 -0600

-----Original Message-----
From: Jeff Hill [mailto:[email protected]] 
Sent: Thursday, June 11, 2009 6:24 PM
To: 'Zhou, Jingchen'
Cc: 'Ralph Lange'; 'Dirk Zimoch'
Subject: RE: PV gateway

> ../../../../src/cas/io/bsdSocket/casDGIntfIO.cc: CA beacon 
> (send to "172.21.40.20:5081") error was "Connection refused"

It's possible to "connect" a UDP socket to a particular { address, port }
destination. When sending a beacon to each of the configured destinations
the server "connects" to that destination briefly so that it can discover
what local address will be the source of this datagram. This is necessary
because when there are multiple network interfaces it's not always clear
which one will be used by the routing system, and the server needs to
include the source address in the protocol (long story). A probably
beneficial side effect is that there are nice diagnostic messages when there
are routing problems with the beacons.

So for some reason the server is unable to use "172.21.40.20:5081" as a
destination address. Is the gateway running on "172.21.40.20"? If so, then
maybe there is your answer. You may not have a ca repeater listening at
"172.21.40.20:5081" and so the routing system knows definitively (because
the communication is all within the same host) that beacons can't be sent to
that address. It may be necessary to be more judicious about how the beacon
address list for the GW's server is configured. Note when setting up the
beacon address list that you are effectively configuring the server to send
beacons to multiple CA repeaters (who forward the beacon messages to any
clients that are running on the same machine as the CA repeater).

> 1) do I have to use the default ports for gateway?

There isn't a restriction like that, but configuration of the gateway is
complex. Keep in mind that you are configuring both a client and a server.
When configuring the gateway always use the EPICS_CAS_XXXX variables when
you intend to change the server's configuration, have a close look at the
gateway doc, and also the configuration related documentation in the CA
reference manual.

I have cc'd Ralph and Dirk who have set up some complex EPICS systems with
lots of gateways. I think that Ernest there at SLAC has some experience in
this area also.

> P.S. I am running gateway on RHEL4.

As I recall, there were some Linux specific issues fixed in the past related
to connecting UDP sockets, but haven't heard of any issues recently in this
area.

Jeff

> -----Original Message-----
> From: Zhou, Jingchen [mailto:[email protected]]
> Sent: Thursday, June 11, 2009 4:18 PM
> To: [email protected]
> Subject: RE: PV gateway
> 
> Interesting, when I try the default ports (5064 and 5065), the gateway
> works. My question is that
> 1) do I have to use the default ports for gateway?
> 2) If I can use other ports, why do 5080 & 5081 not work? What is so
> special about these two ports?
> 
> P.S. I am running gateway on RHEL4.
> 
> Thanks,
> Jingchen
> 
> -----Original Message-----
> From: Zhou, Jingchen
> Sent: Thursday, June 11, 2009 12:35 PM
> To: '[email protected]'
> Subject: FW: PV gateway
> 
> Hi Jeff,
> 
> I happened to see this messages:
> 
> http://www.aps.anl.gov/epics/tech-talk/2007/msg01606.php
> 
> I am using R3.14.10. Why do I still have this problem?
> 
> P.S. There is a firewall, which is however configured to allow all
> traffics and ports between two subnets.
> 
> Thanks,
> Jingchen
> 
> -----Original Message-----
> From: [email protected] [mailto:[email protected]]
> On Behalf Of Zhou, Jingchen
> Sent: Thursday, June 11, 2009 12:09 PM
> To: [email protected]
> Subject: PV gateway
> 
> I have set up a PV gateway, and the gateway is built against EPICS Base
> R3.14.10.  When I brought up the gateway, I saw the following errors
> scrolling up in the log:
> 
> ...
> 
> ../../../../src/cas/io/bsdSocket/casDGIntfIO.cc: CA beacon (send to
> "172.21.40.20:5081") error was "Connection refused"
> 
> Jun 11 11:44:57 !!! Errlog message received (message is above)
> ../../../../src/cas/io/bsdSocket/casDGIntfIO.cc: CA beacon (send to
> "172.21.40.20:5081") error was "Connection refused"
> 
> ...
> 
> The gateway was up, but not functional at all, I checked the gateway
> diagnostic panel, nothing was connected, including the gateway's internal
> PVs.
> 
> Any idea?
> 
> Thanks,
> Jingchen
> 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System