Is there any easy way to detect if a port is already being used,
before attempting to bind to it ...
This sounds like a bad idea to me, because it automatically
introduces a race condition between the time you check that the port
is available and the time that you bind. Given that this race
exists, you bind code has to handle "port is use" errors cleanly.
And, given that, you might as well not both checking in advance.
Still, I assume you've thought about this, so I'll answer your direct
question. No, there is no direct method for doing this. While I can
hardly claim to be an authority on sockets, my guess is that the
folks who designed the API didn't include such a method because of
the above-mentioned race condition.
There are, however, numerous indirect methods to do it, but none of
them are ideal. You could, for example, attempt to connect (or, for
UDP, send to) the port and look at the error you get back.
Alternatively, you could list the open ports and search that list.
Techniques for doing this were covered in the recent thread on this
mailing list entitled "how to enumerate TCP and UDP listeners".
S+E
--
Quinn "The Eskimo!" <http://www.apple.com/developer/>
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
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