socket-module: different behaviour on windows / unix when a timeout is set

Mirko Vogt lists at nanl.de
Wed Jul 9 20:02:56 CEST 2008


Hey,

it seems that the socket-module behaves differently on unix / windows when a timeout is set.
Here an example:

# test.py

import socket
sock=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
print 'trying to connect...'
sock.connect(('127.0.0.1',9999))
print 'connected!'


# executed on windows

>C:\Python25\python.exe test.py
trying to connect...
Traceback (most recent call last):
  File "test.py", line 4, in <module>
    sock.connect(('127.0.0.1',9999))
  File "<string>", line 1, in connect
socket.error: (10061, 'Connection refused')
>


# executed on linux

$ python test.py 
trying to connect...
Traceback (most recent call last):
  File "test.py", line 4, in <module>
    sock.connect(('127.0.0.1',9999))
  File "<string>", line 1, in connect
socket.error: (111, 'Connection refused')
$


Even if the error-codes are different both raise an socket.error with the message 'Connection refused' - good so far.
Now I will change the code slightly - to be precise I set a timeout on the socket:


# test.py

import socket
sock=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
sock.settimeout(3.0) # <----------------------------------------------------------
print 'trying to connect...'
sock.connect(('127.0.0.1',9999))
print 'connected!'


# executed on linux

$ python test.py 
trying to connect...
Traceback (most recent call last):
  File "test.py", line 5, in <module>
    sock.connect(('127.0.0.1',9999))
  File "<string>", line 1, in connect
socket.error: (111, 'Connection refused')
$


# executed on windows

>C:\Python25\python.exe test.py
trying to connect...
connected!
>


The code executed by python running on windows does *not* raise the exception anymore.
The Linux does as expected.

Is that behaviour common or even documented? Found nothing.

It took me lot's of time to figure this out, because there was no exception which was raised when testing for open / ports.

When I try to read from the socket (e.g. on port 9999 on which nothing runs) I get a timeout after the via settimeou() specified value.

Thanks in advance,

Mirko



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