CCIE Links and details for simulator

CCIE Tutorials and Simulator
CCIE Tutorials
Simulators for Routers and switches CCNA/CCIE

Newbie's Linux Manual: How Do I Create, Compile And Run a C Program?

Newbie's Linux Manual: How Do I Create, Compile And Run a C Program?: "Here's a detailed discussion of the line above:

1. gcc (GNU C Compiler) is passed...
2. ...-o which means give the executable the name that follows (i.e. myprog)...
3. ...and the program to compile (referred to as the 'source code') is firstprog.c.

- 5 -

To run the program, enter:

./myprog"

Telnet Connection Procedure

first connect to telnet by .
telnet [mail server address] port address.
helo [mail server address]
mail from:
rcpt to:
data: what ever data is to be transfered
.

it will exit and give an acknowledgment number

Connection With Yahoo Server and communication Commands

Now Click on connect. Once you're connected to the mail server, the mail server will respond with something like this:

220 smtp017.mail.yahoo.com ready.
Now we need to introduce ourselves to the computer and specify the sender's address. Technically, it is possible to use any SMTP server to send a mail with any server's name as the sender. This is called "Message Relaying". Since almost all servers have this feature turned off, we will simply type in the name of the SMTP server itself. [Note that you will not be able to see what you type.]
HELO smtp.mail.yahoo.com

The server will respond with:

250 Hello smtp.mail.yahoo.com, pleased to meet you.

Now we specify the sender:

MAIL From:
The server replies:

250 ... OK

There are a few observations to be made here - note that you can specify any sender here. So if you wanted to cheat the server and send bogus mail, the SMTP will not stop you - it has no security provisions. To add security, they combine the SMTP with POP authentication. So, you will have to login using the POP protocol once before using SMTP. [see Dec 2001 issue for POP mail]
Also note that whenever the server sends a message, there's a 3 digit code along with it.
For example, when it sends 250, it means that the Transaction's okay. If it's 220, it means Service Ready. If it's 500, it means there's been a syntax error in the command that you sent, and so on. There's lots of these codes, each having a specific meaning.
This is a very useful thing, as mail program using the protocol will not need to read any of the English text - they will simply read the code to understand what the response is.
Now we type in the recipient and the data, and then quit:

RCPT To:

250 ... Recipient ok

DATA

354 Enter mail, end with "." on a line by itself
From: anaplexian@yahoo.com
To: anaplexian@yahoo.com
Subject: Hi there!
This is a test message!
.
250 Mail accepted

QUIT
221 smtp.mail.yahoo.com delivering mail
[connection closed]

Reference:telnet to send mail by smtp
Also visit for telnet gmail problems
tutorials se