Hi there
how to configure telnet server that when some client connects to my machine i run some script i did and bind the output to him.
thanx

You could set the shell of their account to a C program that runs your script. (I don't believe a script can be a shell, but I might be wrong.)

Are you absolutely sure you want to run a telnet server at all? Use of a telnet server is not considered secure because it's not encrypted.

I'm guessing that what you really want is for the remote user to use telnet, but he never actually logs into a shell. Instead, you just want a custom script to run and spit some output back at the remote user. Is that right? I don't know how to do that purely with bash scripts, but it's easy to use any general purpose programming language to create a simple daemon program that listens to a TCP port and runs a script whenever someone connects to it.