Telnet Unleashed

This is useful for those who want to learn how to use telnet.

Introducing Telnet:

Telnet is a utility that allows one computer to establish connection to another computer. The computer that establishes the connection is referred to as local computer. The computer accepting the connection is referred to as remote or host computer. It allows you to log on to a remote computer, facilitating access to programs, data and any other resources available on the host computer.

It is a terminal emulation program for TCP/IP networks like the Internet. When the client computer establishes a connection with the server computer, you can enter commands through the telnet program and these will be executed on the server. Thus you can control the server and also communicate with other servers on the network.

How to use it? :

1. Open the Telnet program by either from the command line or from the Windows directory.
2. On the Connect menu, click Remote System.
3. In Host Name, type or select the name of the remote system you want to connect to.
4. In Port, type or select the port or service.
5. In Term Type, type or select a string to be used if your host uses Term Type sub negotiation.

If you have a shell account then you can make a connection to it by typing the URL in place of Host Name. A shell account is basically a Unix terminal where you can run applications and do other cool stuff. It would be the best way to learn Telnet and Unix. You should contact your ISP to find more about your shell account.

You can also try telnetting to an FTP server. You can use the facilities of FTP to download files and do other stuff. If you want to connect to an FTP server then type in the name of the FTP site e.g. ftp.yourftpsite.com in the host name and in the port field type in 21. Port 21 is used for FTP service. After doing all that click ‘Connect.’

ISP’s usually have an FTP server that you can access. If your ISP has one then you can access it by typing the domain of your ISP in the host field and type in the port as 21.

If you connect to an FTP server, you will see a prompt with the daemon name and version. A daemon is a program that runs on a remote computer and manages a particular service.

You would be asked to input your username and password. Type in Anonymous as the Username and your e-mail address as the Password for anonymous login. The e-mail address is provided as a courtesy to the webmaster or the owner of the FTP server.

Services :

Try out the following ports:

Services Port Description

FTP - 21 FTP port
Telnet - 23 The default telnet port. This is used for system admin.
Mail - 25 This port is for sending-mail, the Unix mail-sending daemon.
Finger - 79 Used for 'fingering' email accounts, which gives you info on people who have email
accounts on that server.
HTTP - 80 HTTP port used to browse web sites.
POP3 - 110 The port in charge of the daemon to receive mail. Contrast this with 25, the port for
the sending-mail daemon. Don't confuse the two.
News - 119 The port in charge of the news daemon.
Some Tips:

1. You can copy all the text in the Telnet window from the Edit Menu by selecting all and copying.
2. You can change the font by clicking on the Terminal Menu and then in the Preferences click Fonts.
3. You can also change the background color by clicking Background Color in the Preferences.
4. You can set the terminal emulation in the Preferences. If you don’t know which terminal emulation to use then you can use VT-100 (ANSI).
5. You can set the buffer size in order to see the previous lines by scrolling to the top. If you want to see more lines then you can increase the buffer size. The range is usually between 25 to 399.
6. You can enable terminal logging. This is used to capture the screen output of a Telnet session to a text file.

Reference:

Telnet Documentation
Warlock’s Tutorial and
Ashar’s Tutorial

port 25 is also an SMTP server which means that it does secure e-mail...and can forward e-mail...and is not POP2 or POP3

Quote:

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Originally posted here by dohedo
port 25 is also an SMTP server which means that it does secure e-mail...and can forward e-mail...and is not POP2 or POP3

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SMTP stands for Simple Mail Transfer protocol. How does that mean it secures email?? It would only be secure if it's using SSL (Secure Socket Layer) or another encryption scheme.

POP stands for Post Office Protocol, and has nothing to do with port 25 or sending mail.

When you send mail, you use SMTP. (not the only way)
When you receive mail, you use POP. (again, not the only way)

--Sudo

The only thing most users need to know about telnet is not to use it because it transmits passwords in plain unencrypted text that can be intercepted or sniffed. Ssh is far more secure, and frankly there isn't much reason for anybody to be using telnet anymore.

Sorry problemchild, I use Telnet all the time, I just happen to know enough to only use it on my internal non-routable network. (I could walk to the wiring closet, but I don't know where it is.)

For you Windows people try PuTTy. Good client and does use the Secure Shell.

Yeah Putty is a popular client. I like it alot. Nice interface. I also use telnet alot and fine it works like a charm. Nice tutorial and you gave reference to other tutorial's.

Ah... PuTTy.. what a great program. It has many features that the standard windoze telnet does not have.. and once again it does use Ssh (if you specify it). Thx for the tut. I enjoyed reading it! :D

If you just type anonymous on an ftp connection using telnet, the server will not recognise your request. you must use "user anonymous" your then promped for your password which must be answered "pass [email protected]" you cannot enter commands without the proper prefix either. telnet makes a very poor ftp client.

It does make an excellent tool for learning more about the smtp or pop protocols, but for forging your better off setting up the phony acct in your mail client.

A lot of nice stuff about changeing the telnet enviroment. Thats not normally seen. Nice job

Generally, if I have to remotely access a network, I ensure that the network is running SSH2 so I can access it securely. To do so, I generally use SecureCRT. I used to use telnet to access my campus's network, but once I figured out how insecure it is, I stopped going in. I'm currently working with the admins to set up a SSH2 server, but it's a slow process because they don't see that there's any real need for it.

Anyway, good tutorial, hollow_man.

AJ

Quote:

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When you send mail, you use SMTP. (not the only way)
When you receive mail, you use POP. (again, not the only way)

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not entirely true

several pop3 services implement a feature that allows you to send mail; with the XTND XMIT command. i don't know of any clientware that utilizes this - but i thought it would be useful info since we're on the topic of telnet transactions.