A Real World Client Server Application in Delphi

The entire server code should now look something like this:

unit ServU;

interface

uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics,
Controls, Forms,

  Dialogs, IdBaseComponent, IdComponent, IdCustomTCPServer,
IdTCPServer,

  StdCtrls,idContext, IdIntercept, IdServerInterceptLogBase,

  IdServerInterceptLogFile,idSync;

type

 TClientinfo = class(TIdContext)

        public

            IP: String;

            cname: String;

            procedure SendResponse(const Clientname: String;
const AResponse: String);

        end;

           TWriteResponse = class(TIdSync)

        protected

            FMsg: String;

            procedure DoSynchronize; override;

        public

            constructor Create(const AResponse: String);

            class procedure AddResponse(const AResponse: String);

        end;

  TForm1 = class(TForm)

    Memo1: TMemo;

    IdTCPServer1: TIdTCPServer;

    IdServerInterceptLogFile1: TIdServerInterceptLogFile;

    procedure IdTCPServer1Connect(AContext: TIdContext);

    procedure IdTCPServer1Disconnect(AContext: TIdContext);

    procedure IdTCPServer1Execute(AContext: TIdContext);

    constructor Create(AOwner: TComponent);override;

    procedure FormClose(Sender: TObject; var Action:
TCloseAction);

    procedure FormCloseQuery(Sender: TObject; var CanClose:
Boolean);

    procedure FormShow(Sender: TObject);

  private

    { Private declarations }

  public

    { Public declarations }

  end;

var

  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.IdTCPServer1Connect(AContext: TIdContext);

begin

with TClientinfo(AContext) do

        begin

            if (Connection.Socket <> nil) then

            IP :=Connection.Socket.Binding.PeerIP;

            cname := Connection.IOHandler.ReadLn;

            if cname <> ''then

            begin

            connection.IOHandler.WriteLn('Welcome '+ cname);

            end

            else

            //Client did not send a name...

            begin

            connection.IOHandler.WriteLn('You did not send a
name. Please send a name next time you try to connect!');

            connection.Disconnect;

            end;

end;        end;

procedure TForm1.IdTCPServer1Disconnect(AContext: TIdContext);

begin

TWriteResponse.AddResponse(TClientinfo(AContext).cname + '
Disconnected');

end;

procedure TForm1.IdTCPServer1Execute(AContext: TIdContext);

var

thedate,request,cmd,response,AFormat,sentfrom:string;

i,j:integer;

arr:Array[1..6] of String;

begin

//the request from the client is received in the request var

request:=acontext.Connection.IOHandler.ReadLn;

// we need to break the request up into command(cmd) and sender
(sentfrom)

//showmessage(request);

i:=pos('@',request);

j:=pos(';',request);

cmd:= Copy(request,1,i-1);

sentfrom := Copy(request,i+1,j-i-1);

//showmessage(cmd+'===>'+sentfrom);

  //Check which command the client sent

 if cmd='aquote' then begin

 Randomize;

  arr[1]:='I still miss my ex, but my aim is improving';

  arr[2]:='Last night I was looking up at the stars and I was
wondering, where the heck is my ceiling?';

  arr[3]:='Do Roman paramedics refer to IVs are fours?';

  arr[4]:='I can resist everything except temptation.';

  arr[5]:='There is one thing I would break up over and that is
if she caught me with another woman. I wouldn''t stand for
that.';

  arr[6]:='I''ve often thought that the process of aging could be
slowed down if it had to go through Congress.';

  i:=1+ Random(6);

 //Send the response to the client...

TClientinfo(AContext).SendResponse(sentfrom,arr[i]);

    end

    else

    if cmd='adate' then begin

    AFormat := 'yyyy-mm-dd hh:nn:ss';

    thedate:=FormatDateTime(AFormat, Now);

    TClientinfo(AContext).SendResponse(sentfrom,thedate);

    end

    else

    if cmd='quit' then begin

    TClientinfo(AContext).Connection.Disconnect;

    end

    else

    begin

    TClientinfo(AContext).SendResponse(sentfrom,'Unknown
Command');

    end;

end;

procedure TClientInfo.SendResponse(const Clientname: String;
const AResponse: String);

    var

        List: TList;

        Context: TClientInfo;

        I: Integer;

    begin

       // FContextList is inherited from TIdContext

        List := FContextList.LockList;

        try

            for I := 0 to List.Count-1 do

            begin

                Context := TClientInfo(List[I]);

                if Context.cname = clientname then

                begin

                    try

        Context.Connection.IOHandler.WriteLn(AResponse);

  except

                    end;

                    Exit;

                end;

            end;

        finally

            FContextList.UnlockList;

        end;

        Self.Connection.IOHandler.WriteLn('this server cannot
find the client you sent the message to.');

    end;

constructor TWriteResponse.Create(const AResponse: String);

    begin

        FMsg := AResponse;

        inherited Create;

    end;

procedure TWriteResponse.DoSynchronize;

     begin

form1.memo1.Lines.Add(FMsg);

end;

class procedure TWriteResponse.AddResponse (const AResponse:
String);

  begin

    with Create(AResponse) do try

            Synchronize;

        finally

            Free;

        end;

    end;

   constructor TForm1.Create(AOwner: TComponent);

    begin

        inherited Create(AOwner);

        idTCPServer1.ContextClass := TClientinfo;

    end;

procedure TForm1.FormClose(Sender: TObject; var Action:
TCloseAction);

begin

//idtcpserver1.Active:=false;

end;

procedure TForm1.FormCloseQuery(Sender: TObject; var CanClose:
Boolean);

begin

idtcpserver1.Active:=false;

end;

procedure TForm1.FormShow(Sender: TObject);

begin

idtcpserver1.Active:=true;

end;

end.

Conclusion

The code I use here is generic and can be applied to any client server scenario that meets the inherent requirements of a client server environment. So please use it as a template when implementing your own client server applications. I must once again thank the users at the Delphi newsgroups and also the writers of Indy in Depth who made some excellent reference material available.