[Python-bugs-list] [ python-Bugs-610692 ] telnetlib.py exception in process_rawq

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Bugs item #610692, was opened at 2002-09-18 02:13
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=610692&group_id=5470

Category: Python Library
Group: Python 2.2.1
Status: Open
Resolution: None
Priority: 5
Submitted By: Andrew Williams (andreww5)
Assigned to: Nobody/Anonymous (nobody)
Summary: telnetlib.py exception in process_rawq

Initial Comment:
An unrecognised IAC in the process_rawq method in 
telnetlib.py throws an exception. The final 'else' clause 
in the if/elif structure uses a local variable ('opt') that is 
guaranteed not to have been assigned if that block is 
executed.

In versions 2.2 and up, the offending lines look like:

c = self.rawq_getchar()
...
if c == IAC:
  buf = buf + c
elif c in (DO, DONT):
  opt = self.rawq_getchar()
  ...
elif  c in (WILL, WONT):
  opt = self.rawq_getchar()
  ...
else:
  self.msg('IAC %d not recognized' % ord(opt))


The 1.5.2 and 2.1 telnetlib.py work, becuase the if/elif 
structure ends with

else:
  self.msg('IAC %s not recognized' % `c`)

Changing that line in the new code to refer to 'c' instead 
of 'opt' seems to fix the problem (and looks like what 
you want to report anyway, although I don't understand 
the telnet protocol).

It looks like it's only a problem with wierd telnet servers -
 in particular, an LP-Mud based system on port 4242 at 
flame.ucc.gu.uwa.edu.au, if you want to reproduce the 
bug.

I've attached a program that demonstrates the exception 
(it happens after successful login - choose an initial 
username or use 'test'). 

The same exception happens in windows, MacOS X, 
and unix, although CR/LF issues cause a few problems 
actually logging in under windows.

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