Delphi: DDE call from Indy TCPServer Thread

问题

I try to connect to (Uni)DDE server from an Indy TCP Server thread. From normal application I can connect, and can get/set any PLC variables.

But when I use same command from Indy thread (from Execute(AThread: TIdPeerThread) event), the SetLink command failed.

procedure ReadDDE(AppPath, Service, Topic, Cmd: string; out Eredmeny : string; out HibaSzint : string);
var
    DDE: TDDEClientConv;
    pc : PChar;
begin
    Eredmeny := '';
    HibaSzint := '';
    DDE := TDDEClientConv.Create(nil);
    try
        DDE.ConnectMode := ddeAutomatic;
        DDE.ServiceApplication := AppPath;
        DDE.FormatChars := False;
        HibaSzint := 'SetLink';
        if DDE.SetLink(Service, Topic) then begin
            HibaSzint := '';
            pc := DDE.RequestData(PChar(Cmd));
            Eredmeny := StrPas(pc);
            StrDispose(pc);
        end;
   finally
        DDE.Free;
   end;
end;

Maybe the DDE is using Windows messages, or other things are not threadsafe, or not catchable in the thread's level?

Thanks for any info about this: dd

回答1:

DDE is built on top of windows messages. You need to make sure that messages are dispatched on the thread that has the DDE connection.

回答2:

I know it is too late but may be someone need this instruction. I have worked too many works on it. I have the same problem (but openlink method, not on Set Link method. I used connection mode ddeManual not automatic).At last I found something. Delphi ddeMgr is in the VCL Unit and it needs to be called in like Synchronize(yourProcedure). When I write another procedure (that procedure include my all dde interactions) and in the threads Execute method, I called my procedure with Synchronize. My code look like this.

procedure TAskYTSThread.MakeDDEConv;
begin
 with TDDEClientConv.Create(Form1) do
 begin
    ConnectMode:=ddeManual;
    ServiceApplication:='explorer.exe';
    SetLink('Folders', 'AppProperties') ;
    Form1.Memo1.Lines.Add('Openlink çağrılacak Gönderilecek.');
    if OpenLink then
    begin
      Form1.Memo1.Lines.Add('Link Open Edildi.');
      ExecuteMacro('[FindFolder(, C:\)]', False) ;
      CloseLink;
    end
    else
    begin
      Form1.Memo1.Lines.Add('OLMADIIIIIII');
    end;
    Free;
  end;
end;

procedure TAskYTSThread.Execute;
var
  blnRunning : boolean ;
  FYtsTopicName, strMacro : string ;
begin
  inherited;
  FDDE_BUSY.Enter ;
  try
    blnRunning := IsYTSRunning;
    Synchronize(MakeDDEConv); // this is key point

  finally
    FDDE_BUSY.Leave ;
  end;
end;

I wish this information help other people :)

来源：https://stackoverflow.com/questions/15066705/delphi-dde-call-from-indy-tcpserver-thread