Experimental Physics and
Industrial Control System

"Mark Rivers" <[email protected]> · Tue, 17 May 2011 09:38:38 -0500

I'm a bit confused here.

I run multiple IOCs on my Linux server all the time, without doing
anything special with the ports.  I do see this message after iocInit()
when starting IOCs after the first one:

**********************************
cas warning: Configured TCP port was unavailable.
cas warning: Using dynamically assigned TCP port 58629,
cas warning: but now two or more servers share the same UDP port.
cas warning: Depending on your IP kernel this server may not be
cas warning: reachable with UDP unicast (a host's IP in
EPICS_CA_ADDR_LIST)
**********************************

However, channel access clients have no trouble connecting to PVs in any
of those IOCs.

This is Fedora Core 9.

Do more recent Linux kernels have a problem with this?

Mark

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Claude Saunders
Sent: Tuesday, May 17, 2011 9:02 AM
To: [email protected]
Subject: Re: Channel Access not connecting

Hi Bruce,

 From your first sentence, I see "IOC's" (plural) and "linux". I 
recently had what I believe is the same problem, which Andrew Johnson 
kindly helped me understand. If you are running two iocs on one linux 
host, using default ports, you wind up with two processes listening on 
the same udp port. I gather with linux, the network stack will only 
deliver an incoming (pv search) broadcast UDP packet to one of those 
processes. If it happens to be the one without the PV you're looking 
for, then the ca_search fails, even though the other IOC process 
contains the PV.

    - Claude

On 05/17/2011 12:12 AM, Bruce Hill wrote:
> I've been having trouble with one linux machine where my IOC's appear
> to be running correctly, dbgf works from iocsh, but caget from another
> window on the same machine fails to connect.     I suspect it has 
> something
> to do with how the multiple interfaces on this machine are configured,

> but
> so far have been unable to find a solution.
>
> # ifconfig
> eth0      Link encap:Ethernet  HWaddr 00:1E:68:79:5C:4E          inet 
> addr:134.79.32.161  Bcast:134.79.35.255  Mask:255.255.252.0
>          inet6 addr: fe80::21e:68ff:fe79:5c4e/64 Scope:Link
>          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>          RX packets:190759 errors:0 dropped:0 overruns:0 frame:0
>          TX packets:43567 errors:0 dropped:0 overruns:0 carrier:0
>          collisions:0 txqueuelen:1000
>          RX bytes:18427912 (17.5 MiB)  TX bytes:9772031 (9.3 MiB)
>          Interrupt:19
>
> eth2      Link encap:Ethernet  HWaddr 00:1E:68:79:5C:50          inet 
> addr:192.168.254.2  Bcast:192.168.254.255  Mask:255.255.255.0
>          inet6 addr: fe80::21e:68ff:fe79:5c50/64 Scope:Link
>          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>          RX packets:1238443 errors:0 dropped:0 overruns:0 frame:0
>          TX packets:879202 errors:0 dropped:0 overruns:0 carrier:0
>          collisions:0 txqueuelen:1000
>          RX bytes:80539799 (76.8 MiB)  TX bytes:64420869 (61.4 MiB)
>          Interrupt:20 Base address:0x4000
>
> Gateway is 134.79.35.1
>
> I'm running with defaults for the EPICS_CA* and EPICS_CAS* env
variables,
> but have also played with EPICS_CA_ADDR_LIST, EPICS_CA_AUTO_ADDR_LIST,
> and EPICS_CA_INTF_ADDR_LIST with no success.
>
> See attached files for casr, epicsEnvShow, ifconfig, and netstat
output
> for more configuration details.     We're running base 3.14.9 
> everywhere, but this
> is the only machine showing this problem.
>
> The casr output includes:
> UDP Server:
> UDP 0.0.0.0:0(): User="", V4.0, 0 Channels, Priority=0
>
> This looks wrong to me, as my working IOC's show a valid UDP addr, but

> I'm
> not sure how to fix this, or even if this is the root problem.
>
> Any suggestions would be appreciated.
> Thanks,
> - Bruce
>
> P.S.  When I run caget, tcpdump shows:
> # /usr/sbin/tcpdump -i eth0  -n -nn udp dst portrange 5064-5065
> tcpdump: verbose output suppressed, use -v or -vv for full protocol 
> decode
> listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
> 21:46:55.934345 IP 192.168.254.2.54260 > 134.79.35.255.5065: UDP, 
> length 16
> 21:46:57.179960 IP 134.79.32.161.43268 > 134.79.35.255.5064: UDP, 
> length 48
> 21:46:57.211939 IP 134.79.32.161.43268 > 134.79.35.255.5064: UDP, 
> length 48
> 21:46:57.275932 IP 134.79.32.161.43268 > 134.79.35.255.5064: UDP, 
> length 48
> 21:46:57.403935 IP 134.79.32.161.43268 > 134.79.35.255.5064: UDP, 
> length 48
>

-- 
----------------------------------------------------------
  Claude Saunders<[email protected]>
  Software Services Group Leader
  Advanced Photon Source,   Argonne National Laboratory
  Argonne, IL  60439                   630 - 252 - 6619
----------------------------------------------------------
     We write suggestions, suggesting fading to silence
     And that must please you
     My mirror's tarnished with 'no help'
                       - Gary Numan
----------------------------------------------------------

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System