[Tutor] Basic telnet question

[David Rock]

> On Sep 24, 2016, at 15:49, Phil <phil_lor at bigpond.com> wrote:
> 
> On 25/09/16 01:01, David Rock wrote:
>> 
>> when you say "the client is not responding, certainly not as expected”, what, exactly, is the output you get?
>> 
> 
> In my dazed state I think I responded to David personally instead of the list, my apologies.

:-)

> Thank you for your reply David.
> 
> This is what I expect:
> 
> Trying 127.0.0.1...
> Connected to localhost.
> Escape character is '^]'.
> 
> But, as I say, the console is blocked and nothing is returned.
> 
> I'll try the debug method that you suggested.


So you are expecting to read until the header stanza is complete, then send a command and presumably get the results of the command.
The problem is read_all() doesn’t work the way you think it does.  See what happens with your current code if you send ctrl+], it will probably print as expected, but also close the connection. I don’t think read_all is the right function for the task you are trying to perform.

You are putting it inside a print statement

print(tn.read_all())

but that’s never going to print anything or return control because read_all will never finish (and never return to the print call).  read_all() is a blocking operation that’s going to sit there and keep trying to read data until it’s told to stop (EOF), or until the connection times out.  What you probably mean to do is use read_until().  You know what you are expecting, so try to catch it with something like:

header = tn.read_until("character is '^]’.”, timeout=5)
print(header)
tn.write("f" + "\n”)
etc

read_until looks for a specific string and returns when it finds it, giving control back to you.  


— 
David Rock
david at graniteweb.com