Looking for an alternative to windows messages used in inter-process communication

Question

I a have a multithread application (MIDAS) that makes uses of windows messages to communicate with itself.

MAIN FORM

The main form receives windows messages

Answer 1

Use Named Pipes. If you don't know how to use them, then now is the time to learn.

With named pipes, you can send any type of data structure (as long as both the server and the client know what that data structure is). I usually use an array of records to send large collections of info back and forth. Very handy.

I use Russell Libby's free (and open-source) named pipe components. Comes with a TPipeServer and a TPipeClient visual component. They make using named pipes incredibly easy, and named pipes are great for inter-process communication (IPC).

You can get the component here. The description from the source is: // Description : Set of client and server named pipe components for Delphi, as // well a console pipe redirection component.

Also, Russell helped me out on Experts-Exchange with using an older version of this component to work in a console app to send/receive messages over named pipes. This may help as a guide in getting you up and running with using his components. Please note, that in a VCL app or service, you don't need to write your own message loop as I did in this console app.

program CmdClient;
{$APPTYPE CONSOLE}

uses
  Windows, Messages, SysUtils, Pipes;

type
  TPipeEventHandler =  class(TObject)
  public
     procedure  OnPipeSent(Sender: TObject; Pipe: HPIPE; Size: DWORD);
  end;

procedure TPipeEventHandler.OnPipeSent(Sender: TObject; Pipe: HPIPE; Size: DWORD);
begin
  WriteLn('On Pipe Sent has executed!');
end;

var
  lpMsg:         TMsg;
  WideChars:     Array [0..255] of WideChar;
  myString:      String;
  iLength:       Integer;
  pcHandler:     TPipeClient;
  peHandler:     TPipeEventHandler;

begin

  // Create message queue for application
  PeekMessage(lpMsg, 0, WM_USER, WM_USER, PM_NOREMOVE);

  // Create client pipe handler
  pcHandler:=TPipeClient.CreateUnowned;
  // Resource protection
  try
     // Create event handler
     peHandler:=TPipeEventHandler.Create;
     // Resource protection
     try
        // Setup clien pipe
        pcHandler.PipeName:='myNamedPipe';
        pcHandler.ServerName:='.';
        pcHandler.OnPipeSent:=peHandler.OnPipeSent;
        // Resource protection
        try
           // Connect
           if pcHandler.Connect(5000) then
           begin
              // Dispatch messages for pipe client
              while PeekMessage(lpMsg, 0, 0, 0, PM_REMOVE) do DispatchMessage(lpMsg);
              // Setup for send
              myString:='the message I am sending';
              iLength:=Length(myString) + 1;
              StringToWideChar(myString, wideChars, iLength);
              // Send pipe message
              if pcHandler.Write(wideChars, iLength * 2) then
              begin
                 // Flush the pipe buffers
                 pcHandler.FlushPipeBuffers;
                 // Get the message
                 if GetMessage(lpMsg, pcHandler.WindowHandle, 0, 0) then DispatchMessage(lpMsg);
              end;
           end
           else
              // Failed to connect
              WriteLn('Failed to connect to ', pcHandler.PipeName);
        finally
           // Show complete
           Write('Complete...');
           // Delay
           ReadLn;
        end;
     finally
        // Disconnect event handler
        pcHandler.OnPipeSent:=nil;
        // Free event handler
        peHandler.Free;
     end;
  finally
     // Free pipe client
     pcHandler.Free;
  end;

end.