named listening on UDP

[Edward Lewis]

UDP listens where it sends.  It's not the same as TCP.

In TCP a "listening" port will accept an segment from an "unknown" 
remote address and use that to start a connection.  "Known" remote 
addresses are kinda demultiplexed into the right inter-process 
communication bucket (socket in a BSD environment) and buffered 
before being sent into the machine's processing guts.  TCP ports that 
are not willing to accept connections won't handle "unknown" 
remote-sent segments, that's the difference between listening and 
not.  ("Known" means that there is an established connection.)

UDP does not have the concept of a connection or stream, and in BSD 
terminology, all datagrams are delivered to the same socket.  It 
doesn't matter whether the remote address was seen before or not.


At 8:25 -0400 4/4/07, Jeff Lightner wrote:
>Was the original issue misstated?  You said it was "listening" on these
>ports.  Outbound queries wouldn't be "listening" - they'd simply be
>established when needed.

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Edward Lewis                                                +1-571-434-5468
NeuStar

Sarcasm doesn't scale.