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<== Date ==> <== Thread ==>
Subject: Re: Channel access over wireless?
From: Ralph Lange <[email protected]>
To: EPICS Tech-Talk <[email protected]>
Date: Thu, 31 Oct 2013 19:47:04 +0100
Hi Mark,

On 31.10.2013 19:26, Mark Rivers wrote:

I’m confused.  You said:

 

> Setting EPICS_CA_AUTO_ADDRESS=NO suppresses the UDP broadcast

 

But what if I set

 

EPICS_CA_AUTO_ADDR_LIST=NO

EPICS_CA_ADDR_LIST = 164.54.160.255

 

I do this to restrict EPICS_CA_ADDR_LIST to the broadcast address of one of my NICs.  Don’t I still get UDP broadcasts?


Oh, my.
Sorry about the wrong env var names. They are obviously exceeding my memory size...

You are right, of course.
If the IP address happens to be a broadcast address, all hosts on that network (with a matching configuration) will interpret the messages as UDP broadcasts and receive them.

There is no special "broadcast" marker in the UDP packet; the receiving host determines if a packet is a broadcast by comparing it to its own IP address and subnet mask. That's why things act so funny if you mess up your network/subnet configuration.

Again: sorry for my confusion.
~Ralph

References:
Channel access over wireless? Emmanuel Mayssat
Re: Channel access over wireless? Ralph Lange
RE: Channel access over wireless? Mark Rivers
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