ATPS FAV

Sever Side Chat Application with Borland Delphi/Indy
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This article will get you started on building a chat application based on the client/server model. It will be able to handle all of the basics found in chat applications like Microsoft Messenger and others.

A downloadable zip of the COMPLETE source code for the application is available here.

Introduction
Most chat applications are based on a client/server model, i.e. the client logs on to a server, gets a list of other clients who are logged on and sends messages to them. When you decide to join a chat, the software program that you use connects to a server somewhere and allows you to ‘talk’ to other people who are connected to that server.
Our chat application is also going to be based on client/server model. What we are going to do in this tutorial is look at how the server enables clients to communicate. We are also going to look at how the server sends files to other clients, take screenshots and sends these back to your computer. We will set up our own little communication protocol.
Requirements for the Server Application:
We want the server to be able to keep a record of every client on the chat.
We want it to be able to send files and take screenshots of connected clients.
We want it to send text to everybody or a single person (private chat), with the possibility of doing a three way chat.
What you need
You need to have Indy 9 or 10 installed. If you have Delphi 6 or above, then you can skip this section; otherwise go to www.indyproject.org and download the version appropriate to your Delphi version. I am using Delphi 7 and Indy 10.0.52. There are proper guides available on the indy site, on how to install Indy on your computer.
Let's get started!
Fire up Delphi and create a new application. Go to the indy server tab, select and add the idtcpserver (make sure that it is the idtcpserver and NOT the idsimpletcpserver or anything else), then go to the object