[Vm-dev] Socket listening
bert at freudenbergs.de
Tue Jul 1 13:35:23 UTC 2008
Ian, and folks,
I'm trying to write a more robust Etoys server for OLPC, and found
some surprising listening behavior.
The snippet below tries to listen on the same port twice. I'd have
expected to get an error on the second listening attempt. However, on
both Linux and Mac OS X (John's VM) I get back
which means the second socket listens successfully, but on a random
port. I verified it is actually listening there using lsof. The
SO_REUSEADDR option does not make any difference, btw.
So, is this intended behavior? If not, will we change it?
In my actual use case I would have tried to iterate through some ports
to find an unbound one, so in this particular case the behavior is
convenient for me. But I think I should not rely on it. Also, the same
code gives an error (as expected) on Windows.
- Bert -
p := 6060.
s1 := Socket newTCP.
s1 setOption: 'SO_REUSEADDR' value: 0.
s1 listenOn: p.
s2 := Socket newTCP.
s2 setOption: 'SO_REUSEADDR' value: 0.
s2 listenOn: p.
s1 isValid ifTrue: [s1 port].
s2 isValid ifTrue: [s2 port]
] ensure: [
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