[Tutor] Dodgey if loop ?

[nick at javacat.f2s.com]

Hi folks,

I've just wrote a little port scanner, and strangely enough I only have one
problem with it lol .

Here's the offending code:

[code]
pnumber = str(pnumber) #pnumber is 25 for example
for line in f: # f is '/etc/services' open file
    if not line.startswith('#') and len(line) > 10:
        p = line.split()[1].split('/')[0]
            if p == pnumber:
                return line.split()[0] # would return 'smtp'
            #else:
                #return '?'
[/code]

As it stands this works fine.
However, if I uncomment the else loop in the final if loop it will always return
the '?'. Leaving the final else commented out (as above) if pnumber is not in
/etc/services it returns 'None' which I can live with.

Can anyone see why this is happening please ?

Here's a brief session of running the program with the final else commented out:
[nickl at netview socket]$ ./scan.py bishop1 1 1024
Trying bishop1 ...

bishop1 is listening on port 7 (echo)
bishop1 is listening on port 9 (discard)
bishop1 is listening on port 13 (daytime)
bishop1 is listening on port 19 (chargen)
bishop1 is listening on port 21 (ftp)
bishop1 is listening on port 23 (telnet)
bishop1 is listening on port 25 (smtp) ... etc

Here's what happens when I uncomment the final else:
[nickl at netview socket]$ ./scan.py bishop1 1 1024
Trying bishop1 ...

bishop1 is listening on port 7 (?)
bishop1 is listening on port 9 (?)
bishop1 is listening on port 13 (?)
bishop1 is listening on port 19 (?)
bishop1 is listening on port 21 (?)
bishop1 is listening on port 23 (?)
bishop1 is listening on port 25 (?) ... etc

Many thanks
Nick.








 
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