OS independent way to check if a python app is running?

[Dan Sommers]

On Sun, 27 Dec 2009 19:07:12 -0500, python wrote:

> Hans,
> 
>> Unfortunately, Windows is not a respectable OS. Unlike Unix, it allows
>> two processes to bind to the same port. The theory is that this somehow
>> allows the two processes to share their workload. One thing the OP can
>> portably do, is try to connect() to the port. If that succeeds, then a
>> server program is already running at that port, so he should exit.
> 
> Thank you for your tip - spot on!

Beware of the converse, though.  If a process *cannot* connect to the 
port, then it should *not* assume that another server *isn't* running.  
If two potential servers both start at the same time, and each tries to 
connect, then both will fail, but you don't want both to start, either.