OTish: using short-term TCP connections to send to multiple slaves

Roy Smith roy at panix.com
Sun Nov 16 18:21:23 CET 2014


In article <mailman.15887.1416150791.18130.python-list at python.org>,
 Chris Angelico <rosuav at gmail.com> wrote:

> UDP for anything more than your network's MTU is inefficient

Why do you say it's inefficient?  Sure, the UDP datagram will get 
fragmented and re-assembled at the other end, but it's not like TCP 
would do any better.  One way or another, your data is going to be 
transmitted in packet that fit into the MTU.

> plus you'd need to roll your own acknowledgement system so you know 
> when the client got the data, at which point you're basically 
> recreating TCP.

That I certainly agree with.  UDP should be used for fire-and-forget, 
where its not critical that every bit of data gets through.  A classic 
example is high-volume logging.  Once you start thinking about any kind 
of acknowledgements, you should just switch to TCP.  The alternative is 
that you will slowly end up reinventing TCP (and doing a bad job of it).

> NAT is the most common cause of breakage, but any router does have the
> power to monitor and drop connections on any basis it likes. (I can't
> imagine any reason a non-NAT router would want to prevent connections
> from going idle, but it could be done.)

It's common in corporate networks for routers to forcibly close idle 
connections (i.e. inject RST packets).  Often, the IT security guys 
think idle connections represent some kind of threat (and good luck 
trying to argue with them).



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