Telnet

[jvqpDjzh]

Hello!

Does somebody knows how to work with telnet?

I've tried to connect to another computer I have, where I installed the telnet (server): finally, I could make the connection, but when I tried to login and insert the password, it appeared that the connection had been lost: "...Shell process may not have been launched...".

What could be the problems? I have already modified, in services, the type of the program start to "Automatic" in both computers.

(I hope this question is not inappropriate.)

[Computergeek01]

The telnet service only needs to be running on the host that is being connected to. The next step is to add the entry for the telnet port (23) to the firewalls exception\pass-through list and possibly the network protection client of the hosts AV suite. From there, assuming there is a domain trust between the two PC's and the account you are logging in from is part of an appropriate security group, you'll be sent to what ever directory the services interpreter is configured for; by default this interpreter is the command shell.

Telnet is really only used for diagnostic purposes these days. What are you trying to play with? We might have a better tool in mind.

[jvqpDjzh]

So, basically I just have to add the entry for telnet port (23) to the firewalls exception list, possibly in both: server and client, right? (I am using windows7: should I have to go to control pannel > system and security > windows firewall > allowed programs ... and then allow telnet to be used? (sorry if it seems a stupid question)

I am trying to understand how these programs work, what is the power and what can I do useful with such a program.

Can you tell me some useful and serious guides or sites about the argument (and about computer networks, in general)?

I would like to pass to other programs (protocols), but of course I have little experience for now...

What are the better tools you are talking about (Putty)?

[ResidentBiscuit]

I am trying to understand how these programs work, what is the power and what can I do useful with such a program.

Telnet is quite old and mostly not even used anymore. As Computergeek said, it's mainly just diagnostic.

Can you tell me some useful and serious guides or sites about the argument (and about computer networks, in general)?

Argument? Computer networks is a massive topic. There are tons of sub-fields under computer networks that people can spend their entire life specializing in. If you're interested, I suggest grabbing an into level computer networking book and start there.

What are the better tools you are talking about (Putty)?

Putty is nice. Gives you a handful of popular protocols to use. I only ever use it for SSH and serial connections, but it does have telnet and I think one other you can use.

You're best tool right now is grabbing a Linux distro. Networking tasks are infinitely easier in Linux than they are in Windows.

[jvqpDjzh]

I have Ubuntu installed on my computer, in another partition. I have already used it, but just simple things, like installing programs (not with the shell) or using Code::blocks or other IDEs to write C++ sources.

I would like to pass to Linux, but I can't really understand the potencial, the advantages and the utility of using it, and why it's good for networking tasks.

Can you tell me just some guides that can introduce me to the useful world of Linux?
I have read something around, but nothing really convince me...

[MiiNiPaa]

Telnet is quite old and mostly not even used anymore.

Well, it is useful for one thing:
telnet towel.blinkenlights.nl

[nvrmnd]

haha, reminds me of the coolest tutorial i've learned on youtube

[jvqpDjzh]

thank you very much for being serious and help me!

[Computergeek01]

I am trying to understand how these programs work ...

Telnet specifically uses TCP to connect to a service running on another machine. Most of the time that service is a telnet server but I've also connected to SMTP services on port 25, and http services on port 80 etc. Those specific services have standardized protocols so you can look up the commands to send them. If you want to experiment a bit with the smtp protocol the connect use: telnet smtp.outlook.com 25 to connect to the hot-mail server and enter "EHLO" (not a typo) to get a list of commands that it supports. From there you need to send your data encoded or encrypted to do anything else but feel free to look up the documentation if you feel like pursuing that further.

... what is the power and what can I do useful with such a program.

If you can't tell me what you can do with a command shell running on a remote host then you need to play around in local command shell land a bit more. Remember that all of those "super secure" UAC checks that Microsoft likes to brag about? Yeah, they don't happen on that kind of connection. Your level of access is restricted only by the ACE's on that machine and the login that you use. Which by the way is only one reason why nobody in their right mind uses telnet anymore (we actually stopped a good deal before Windows Vista came out) and this is pretty much a dead exploit these days.

EDIT: You don't have to, and in fact you should not, run a telnet server or make a hole for it on the inbound connects for the machine you are connecting from. You may need to add it to the list of exceptions for outbound traffic but that's about it.

[Cubbi]

From there you need to send your data encoded or encrypted

Times sure have changed since I last telnetted to 25 to enter MAIL FROM: [e-mail]

btw, telnet is actually a fairly complex protocol (although aside for losing the '\xff', it is not invoked if you connect to something other than 23), the more straight-to-the point diagnostic tool is nc (netcat)

[jvqpDjzh]

1.

Computergeek01

First of all, thanks!
2.

our level of access is restricted only by the ACE's on that machine and the login that you use.

What is ACE's?
3.

From there you need to send your data encoded or encrypted to do anything

From the hot-mail server, right? (maybe it's just tiredness).
But then what do you mean by the fact that telnet does not encrypt the data (sorry for the ignorance)?
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Cubbi

1.

although aside for losing the '\xff', it is not invoked if you connect to something other than 23

Sorry, I don't understand completely this part...
2.

the more straight-to-the point diagnostic tool is nc (netcat)

I will surely have a look at it! Thank you!

[Computergeek01]

1.) You're welcome

2.) ACE: Access Control List, this is how Windows manages who can do what.

3.) Yes, the smtp server I posted was for hotmail (outlook.com now). You have to encrypt the data before hand and send that. What I mean is that telnet will not do this for you.