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<== Date ==> <== Thread ==>

Subject: Re: Channel Access not connecting
From: Claude Saunders <saunders@aps.anl.gov>
To: tech-talk@aps.anl.gov
Date: Tue, 17 May 2011 09:02:08 -0500
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<saunders@aps.anl.gov>
 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
----------------------------------------------------------


Replies:
RE: Channel Access not connecting Mark Rivers
RE: Channel Access not connecting Jeff Hill
References:
Channel Access not connecting Bruce Hill

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