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    <p>I use named pipes for this, it was the easiest one I found. I'll post the code when I get home from work.</p> <p>Here's an article on how to use it in delphi: <a href="http://www.delphi3000.com/articles/article_2918.asp?SK=" rel="noreferrer">http://www.delphi3000.com/articles/article_2918.asp?SK=</a></p> <p>There's a million solutions to this by the way, all of them seem to be annoying. Pipes is the best one I've found so far.</p> <p>Here's the code, sorry about the delay. You should check out the Pipe library mentioned by Mick too. The thing I've done here was a pretty quick experiment. Please note that it was made in Delphi 2009.</p> <pre><code>unit PetriW.Pipes; interface uses Windows, Classes, Forms, SyncObjs, SysUtils ; type TPBPipeServerReceivedDataEvent = procedure(AData: string) of object; TPBPipeServer = class private type TPBPipeServerThread = class(TThread) private FServer: TPBPipeServer; protected public procedure Execute; override; property Server: TPBPipeServer read FServer; end; private FOnReceivedData: TPBPipeServerReceivedDataEvent; FPath: string; FPipeHandle: THandle; FShutdownEvent: TEvent; FThread: TPBPipeServerThread; protected public constructor Create(APath: string); destructor Destroy; override; property Path: string read FPath; property OnReceivedData: TPBPipeServerReceivedDataEvent read FOnReceivedData write FOnReceivedData; end; TPBPipeClient = class private FPath: string; protected public constructor Create(APath: string); destructor Destroy; override; property Path: string read FPath; procedure SendData(AData: string); overload; class procedure SendData(APath, AData: string); overload; end; implementation const PIPE_MESSAGE_SIZE = $20000; { TPipeServer } constructor TPBPipeServer.Create(APath: string); begin FPath := APath; FShutdownEvent := TEvent.Create(nil, True, False, ''); FPipeHandle := CreateNamedPipe( PWideChar(FPath), PIPE_ACCESS_DUPLEX or FILE_FLAG_OVERLAPPED, PIPE_TYPE_MESSAGE or PIPE_READMODE_MESSAGE or PIPE_WAIT, PIPE_UNLIMITED_INSTANCES, SizeOf(Integer), PIPE_MESSAGE_SIZE, NMPWAIT_USE_DEFAULT_WAIT, nil ); if FPipeHandle = INVALID_HANDLE_VALUE then RaiseLastOSError; FThread := TPBPipeServerThread.Create(true); FThread.FreeOnTerminate := false; FThread.FServer := self; FThread.Resume; end; destructor TPBPipeServer.Destroy; begin FShutdownEvent.SetEvent; FreeAndNil(FThread); CloseHandle(FPipeHandle); FreeAndNil(FShutdownEvent); inherited; end; { TPipeServer.TPipeServerThread } procedure TPBPipeServer.TPBPipeServerThread.Execute; var ConnectEvent, ReadEvent: TEvent; events: THandleObjectArray; opconnect, opread: TOverlapped; Signal: THandleObject; buffer: TBytes; bytesRead, error: Cardinal; begin inherited; //SetThreadName('TPBPipeServer.TPBPipeServerThread'); ConnectEvent := TEvent.Create(nil, False, False, ''); try setlength(events, 2); events[1] := Server.FShutdownEvent; FillMemory(@opconnect, SizeOf(TOverlapped), 0); opconnect.hEvent := ConnectEvent.Handle; while not Terminated do begin ConnectNamedPipe(Server.FPipeHandle, @opconnect); events[0] := ConnectEvent; THandleObject.WaitForMultiple(events, INFINITE, False, Signal); if Signal = ConnectEvent then try // successful connect! ReadEvent := TEvent.Create(nil, True, False, ''); try FillMemory(@opread, SizeOf(TOverlapped), 0); opread.hEvent := ReadEvent.Handle; setlength(buffer, PIPE_MESSAGE_SIZE); if not ReadFile(Server.FPipeHandle, buffer[0], PIPE_MESSAGE_SIZE, bytesRead, @opread) then begin error := GetLastError; if error = ERROR_IO_PENDING then begin if not GetOverlappedResult(Server.FPipeHandle, opread, bytesRead, True) then error := GetLastError else error := ERROR_SUCCESS; end; if error = ERROR_BROKEN_PIPE then // ignore, but discard data bytesRead := 0 else if error = ERROR_SUCCESS then // ignore else RaiseLastOSError(error); end; if (bytesRead &gt; 0) and Assigned(Server.OnReceivedData) then Server.OnReceivedData(TEncoding.Unicode.GetString(buffer, 0, bytesRead)); // Set result to 1 PInteger(@buffer[0])^ := 1; if not WriteFile(Server.FPipeHandle, buffer[0], SizeOf(Integer), bytesRead, @opread) then begin error := GetLastError; if error = ERROR_IO_PENDING then begin if not GetOverlappedResult(Server.FPipeHandle, opread, bytesRead, True) then error := GetLastError else error := ERROR_SUCCESS; end; if error = ERROR_BROKEN_PIPE then // ignore else if error = ERROR_SUCCESS then // ignore else RaiseLastOSError(error); end; finally FreeAndNil(ReadEvent); end; finally DisconnectNamedPipe(Server.FPipeHandle); end else if Signal = Server.FShutdownEvent then begin // server is shutting down! Terminate; end; end; finally FreeAndNil(ConnectEvent); end; end; { TPBPipeClient } constructor TPBPipeClient.Create(APath: string); begin FPath := APath; end; destructor TPBPipeClient.Destroy; begin inherited; end; class procedure TPBPipeClient.SendData(APath, AData: string); var bytesRead: Cardinal; success: Integer; begin if not CallNamedPipe(PWideChar(APath), PWideChar(AData), length(AData) * SizeOf(Char), @success, SizeOf(Integer), bytesRead, NMPWAIT_USE_DEFAULT_WAIT) then RaiseLastOSError; end; procedure TPBPipeClient.SendData(AData: string); var bytesRead: Cardinal; success: boolean; begin if not CallNamedPipe(PWideChar(FPath), PWideChar(AData), length(AData) * SizeOf(Char), @success, SizeOf(Integer), bytesRead, NMPWAIT_USE_DEFAULT_WAIT) then RaiseLastOSError; end; end. </code></pre> <p>Here's how I send something:</p> <pre><code>TPBPipeClient.SendData('\\.\pipe\pipe server E5DE3B9655BE4885ABD5C90196EF0EC5', 'HELLO'); </code></pre> <p>Here's how I read something:</p> <pre><code>procedure TfoMain.FormCreate(Sender: TObject); begin PipeServer := TPBPipeServer.Create('\\.\pipe\pipe server E5DE3B9655BE4885ABD5C90196EF0EC5'); PipeServer.OnReceivedData := PipeDataReceived; end; procedure TfoMain.PipeDataReceived(AData: string); begin if AData = 'HELLO' then // do something, but note that you're not in the main thread, you're in the pipe server thread end; </code></pre>
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    1. POHow do I send a string from one instance of my Delphi program to another?
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    1. COThanks for adding this example. It helps to clarify.
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    2. COThe delphi3000 article link is broken.
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