Experimental Physics and
Industrial Control System

> We occasionally log messages like this on our IOCs:
> Thu Jul 31 10:51:39 2003 ../iocinf.c: bad UDP msg 
> from 172.16.1.105:5124

Gary's message was from the CA server library. Your message originates from the CA client library. Depending on
your version you might also see this message: "Corrupt cmd in UDP msg %u"? If that information is available it
might help to track down the cause.

CA clients operate on ephemeral (dynamically assigned) ports. Therefore it is less likely that this message would
occur because of a configuration error or because of some other system using the EPICS port numbers (because the
port number would change each time that you make a new connection).

It seems that the more likely cause would be excessive multi-bit errors clobbering the packet beyond CRC error
detection thresholds. That might occur if there was excessive noise in the system or if 172.16.1.105 failed its
10/100 Mb auto-negotiation.

A packet dump might also help with resolving the problem.

Jeff

> -----Original Message-----
> From: Brian McAllister [mailto:[email protected]]
> Sent: Tuesday, August 26, 2003 2:33 PM
> To: Jeff Hill
> Cc: 'Gary P Carr'; [email protected]
> Subject: Re: Channel Access Errors
> 
> 
> >>> On 8/25/2003 at 15:33:26 MDT, Jeff Hill wrote:
> 
>   > o Possibly 3rd party software/hardware using UDP port 5064 that
> isn't CA.
> 
> We log messages like this on our IOCs:
> 
> Thu Jul 31 10:51:39 2003 ../iocinf.c: bad UDP msg from 172.16.1.105:5124
> 
> 
> We believe that these are generated by win4lin, a Windows emulator that
> runs on Linux.  They show up occasionally, probably when win4lin is
> started.  We haven't investigated further, as there appears to be no
> impact
> other than the messages.
> 
> ----
> Brian McAllister                    Controls Programmer/Beam Physicist
> [email protected]                        MIT-Bates Linear Accelerator
> (617) 253-9537                                           Middleton, MA

References:

Re: Channel Access Errors Brian McAllister

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