telnet to Cognex In-Sight 4001 camera

square.steve square.steve at
Mon Feb 25 20:24:22 CET 2013

At the risk of stating the blindingly obvious, have you run a 'real' telnet session to see what  a successful conversation looks like? Might give you some useful pointers for your debug session.


Sent from a Galaxy far, far away....

-------- Original message --------
From: chris.annin at 
To: python-list at 
Subject: telnet to Cognex In-Sight 4001 camera 
Hello,  ive been struggling with this for a couple weeks now and was hoping someone might be able to help.  I have an older Cognex camera that I need to communicate with via telnet.  I can get a response from the camera when I initiate a telnet session but I dont seem to get any response when I write the user name to the camera -  I havnt been able to get any response writing anything. Im using python 2.7 and windows xp.  here is the code:
>>>import sys
>>>import telnetlib
>>>HOST = ""
>>>USER = "admin"
>>>tn = telnetlib.Telnet(HOST)
>>>tn.read_until("Login: ")
"Welcome to In-Sight(R) 4001 Session 1\r\nUser:"
>>>tn.write(USER + "\r\n")
>>>tn.read_until("User: ")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python27\lib\", line 319,
    return self.read_very_lazy()
  File "C:\Python27\lib\", line 395,
    raise EOFError, 'telnet connection closed'
EOFError: telnet connection closed

if i do a read_all instead of read_until for user I just get "..." returned.  Im assuming tn.write command isnt working?  any help would be greatly appreciated.

thank you

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