How do I create a Telnet Client inside of a Delphi 5 application?
ICS (Internet Component Suite) by Francois Piette has got some useful components:
http://www.overbyte.be/eng/products/ics.html
It'll give you telnet protocol support, a terminal emulator and some stuff to help you scripting. It's easy to use, and it's all free.
From the site:
TTnCnx - TELNET client protocol support.
TEmulVT - ANSI terminal emulation (like a TMemo but with ANSI escape sequences interpretation).
TTnEmulVT - TELNET and ANSI terminal emulation combined into a single component. You can build a full telnet client program in only a few lines of code.
TTnScript - TELNET scripting component. Used to automate work with telnet session (such as auto login and password).
And there are some example applications to show how to use it:
TnClient - A full featured TELNET client program with ANSI terminal emulation.
TnDemo - A TELNET client using a TMemo to display incoming data.
TnSrv - A basic event-driven server. Can support any number of concurrent clients. The base for any real world server. See also TcpSrv, MtSrv (multi-threaded) and MidWare for a complete client/server framework.
Internet Direct (Indy) and Synapse include Telnet classes.
Both work fine with Delphi up to version 2009 (and with Free Pascal).
Take a look at AsyncPro on SourceForge (previously from Turbopower). It has excellent fax, modem and comms support but note that it is only suitable for all Delphi's up to before D2009 (it's not unicode).
Another option which works very well, and includes full source that is easy to extend and modify, is Synapse. The latest version available from the SVN links on the authors website is updated and supports Delphi 2009, in addition to free pascal/Lazarus.
plus to tcp/socket programming, you must understand how telnet protocol works, for that you can refer to RFC(request for comment) documents
this is telnet specification telnet specification and old telnep protocol rfc
for very pure delphi telnet client/daemon code please check this pack (KOL based)
A telnet application can be done by simply sending string via socket. Use the TSocket**** APIs from Delphi.
来源：https://stackoverflow.com/questions/896069/how-to-create-telnet-client-with-delphi-5