Creating Chat Application with Borland Delphi/Indy: The Client

Add the following in the uses clause of the form (up in the interface section):

jpeg,idsync,IdStreamVCL, INIFiles

Then under the ‘type’ declaration add the following:

TReadingThread = class(TThread)
        protected
            FConn: TIdTCPConnection;
            procedure Execute; override;
        public
            constructor Create(AConn: TIdTCPConnection); reintroduce;
        end;
//you will recognise this bit from the server tutorial
         TLog = class(TIdSync)
        protected
            FMsg: String;
            procedure DoSynchronize; override;
        public
            constructor Create(const AMsg: String);
            class procedure AddMsg(const AMsg: String);
        end;

Basically, these two classes work together to read any messages that get sent by the server; they then parse the messages to the relevant procedures. So any messages that are received by the client are processed by these classes first, before being sent on. They help to make sure that the main VCL thread is not used when messages are received. The TReading class reads the message first and then uses the tlog class to process the message.

In the public section of the form add the following variables:

port: integer;
ip:string;

Then in the form variables add:

rt: TReadingThread = nil;

In the implementation section add:

uses mmsystem,picfrm,setup,sendfile;

function ParseString(s : string; var str1,str2,str3: string) :
boolean;
var
   P1,P2 : integer;
begin
   P1 := Pos('@',s);
   P2 := Pos(';',s);
   //Test if both delimiters are present, in the right order and
   //at least 1 char apart
   if ((P1 > 0) and (P2 > 0) and (P2 > P1) and (Abs(P2-P1) > 1))
     then begin
            str1 := Copy(s,1,P1-1);
            str2 := Copy(s,P1+1,P2-P1-1);
            str3 := Copy(s,P2+1,Length(s)-P2);
            Result := True; //valid string
          end
     else Result := False; //invalid string
end;

I’ve already explained what this function does in the server side tutorial, so I will not go through it here.

constructor TLog.Create(const AMsg: String);
    begin
        FMsg := AMsg;
        inherited Create;
    end;