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bod_1

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Telnet login

Hi,
I'm wondering what UNIX servers send you when you log on.  I wrote an WinSock program that connects to a UNIX (AIX) server.  When I connect, it sends me three bytes:
FF FD 18
I didn't know what to do so I just echoed them back and it sent me three more bytes:
FF FC 18
So I echoed those back as well.
This was good in that it got me the login string but that string was preceded with about ten bytes of non-ASCII characters.
It was a wild guess that got me to the login prompt but I'd like to know what all of this non-ASCII data represents, I was expecting to just get a bunch of strings, carriage returns, and line-feeds...
This is my first socket program.
I have no experience in sockets or programming for networks, just a lot of reading.
Thanks
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shirlng

Have you checked the Port and the Terminal Type from the Remote System?
FF indicates the IAC(interpret as command character).  The next few bytes will be the command and any associated options.  Bascially the telnet process on the AIX server is trying to negotiate some options.  Also normally the AIX tries to clear the screen before presenting the login prompt.  This is done by sending a series of 0x0A characters before the prompt.

For more info. on the telnet protocol, please refer to RFC-854.
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ASKER

Thanks guys,
I the port that I am using is telnet (it is resolved from it's name and corresponding port from some file, I forget it's name right now).  Terminal type ?  Is that what it's doing?  Seeing what kind of terminal I am (dumb, VT...) ?
I got a buch of 0A's (line feed) after that too.  I noticed that while using WS_FTP program, every command echoed to the debug window has a number infront of it.  I suppose these numbers are command codes?
I am looking at RFC now;

Thanks again
WS-FTP will display the commands of the protocol FTP.  
You would not want to confuse that with the telnet protocol you are interested in.
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ASKER

I just installed Linux and got it configured.  man, what I'm looking for will be right on my machine now too.
I have much reading to do.
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David Williams
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ASKER

Cool,
That makes sense.

Thanks for the help guys