Determine if a port is in use/find next available free port

[Malcolm]

Is there an OS independent way to determine is a specific port is in
use?

Scenario: I have a cherrypy based application running as a local
(desktop) server. I have the default port set to 8080, but if this
port is in use, I would like my server to detect this condition and
search for the next free port.

Does anyone have any techniques or code to share that would get me
started?

Thank you,
Malcolm

[João Pinto]

2009/12/14 Malcolm <webm...@awarepro.com>

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Hello you could use the socket module to probe for an available port:

import socket

serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)   
port = 8080
while port < 9000:
    try:
        serversocket.bind(('localhost', port))
        # You may want: serversocket.bind((socket.gethostname(), port))
    except socket.error as e:
        if e.errno==98:
            port = port+1
        else:
            raise
    else:
        break
serversocket.close()
print "Found port", port

--
João Pinto
IRC: joaopinto @ irc.freenode.net
Jabber ID: lamego...@gmail.com
GetDeb Team Leader - http://www.getdeb.net

[Malcolm]

Hi João,

I'm running Python 2.6.4 (32-bit) on Windows 7 Pro (64-bit) and
received the following error when testing your code:

QUOTE: socket.error: [Errno 10048] Only one usage of each socket
address (protocol/network address/port) is normally permitted

I added errno 10048 to your exception handler and your code works
great.

UPDATED SNIPPET:

except socket.error as e:
if e.errno in ( 98, 10048 ):
print 'Port %s is unavailable (%s)' % ( port, e.errno )
port = port+1

Thank you very much for your code - it was a big help!

Regards,
Malcolm