Creating Chat Application with Borland Delphi/Indy: The Client

The TLog/TReading classes are the meat of this application. This is where all the commands or messages coming from the server will be read and processed. When a message arrives from the server, it is stored in the variable called AMsg, then in FMsg as above.

               procedure TLog.DoSynchronize;
              var
             idx:integer;
            cmd,bw,fn,msg:string;
            FStream,fstream2: TFileStream;
            IdStream,idstream2: TIdStreamVCL;
            MStream: TMemoryStream;
               begin
 //find position of @ in  FMsg
//remember the message coming from server will be in format: msg/command@from:to
           idx:=pos('@',FMsg);
//get the command
           cmd:=copy(FMsg,1,idx-1);
 //list of names recieved
           if cmd='list' then  begin
           FMsg:= Copy(FMsg, Pos('@', FMsg)+1, Length(FMsg)-Pos
('@', FMsg));
           form1.lnames.Clear;
           form1.lnames.Items.Add('***Current Members***');
//display the list of names to the listbox
           form1.lnames.Items.Add(FMsg);
           end
//picture have been send
          else if cmd= 'pic' then begin
 // server sends: 'pic@'+fn+':Sending file...'
          parsestring(FMsg,bw,fn,msg);
 //read the file in and save
          MStream := TMemoryStream.Create;
          try
          form1.msg.Lines.Add('Recieving file ' +fn+'...');
      IdStream := TIdStreamVCL.Create(MStream);
      try
      form1.tc.IOHandler.ReadStream(IdStream);
//save file
      mstream.SaveToFile(fn);
//try getting file path to indicate where saved
      form1.msg.Lines.Add('File successfully recieved');
      finally
          IdStream.Free;
      end;
      finally
      MStream.Free;
          end;
          end
          else
//it’s a plain message, just add to the memo
            Form1.msg.lines.add(FMsg);
        end;

In the above code, all that happens is that when the message is received, the procedure extracts the command, which would have been sent from the server. For example, if the server sends a message containing the command pic, then the client would prepare to receive a file. 

              class procedure TLog.AddMsg(const AMsg: String);
              begin
              with Create(AMsg) do try
              Synchronize;
              finally
              Free;
             end;
             end;

            constructor TReadingThread.Create(AConn:
TIdTCPConnection);
            begin
            FConn := AConn;
            inherited Create(False);
            end;

             procedure TReadingThread.Execute;
             begin
            while not Terminated and FConn.Connected do
             begin
 // read msg from server
            TLog.AddMsg(FConn.IOHandler.ReadLn);
            end;
            end;

As previously stated, the three procecures above work together to receive and process the message received from the server.