I have a problem that is causing me to tear out the remaining hairs on
my head.  I am using the TcpServer and TcpClient controls from the
Internet tab in D6 Ent to create a Peer-to-Peer Alert System.  In the
chat demo that comes with D6, they create a thread to update a memo
field with the recieved lines of text that come in.

I tried it without spawning the extra DataThread to update the
memRecv.Lines control, but nothing will update unless the extra
threading is used.  TcpServer is using threads as well.  The problem
comes when I shut the program down.  Everything works great while the
programs are running, alerts come in fine, all is well, but when I
attempt to shut the program down, I get:

The instruction at "0x77f83941" referenced memory at "0x00000010". The
memory could not be "written".

I don't receive this error when the program is closed after being run
from the IDE, only when the exe is run alone.  The error message does
not happen when I use nonblocking mode and no extra threading, but
then I cannot have more than one connection happening at once.  Any
idea's? I am being contracted to do this, and did not anticipate this
sort of block.  It does not affect the performance of the system, but
certainly, I cannot deliver a system that give access violations when
shut down.

Thanks,

Wes

remove the wontbesentjunkmail
to email me

--
Jason Southwell
President & CEO
Arcana Technologies

Wes,

Generally, when an error occurs outside the IDE and not inside, there is
usually a pointer or object that is being misused, or destroyed.

My advise would be to start using Try..Excepts to find exactly where the
problem occurs at, then analyzing what could be happening to that variable.

-Luke

I have included the key events in my prog, could someone just have a
quick scan and confirm that everything is OK in it.

Thanks

Wes

** Not in any specific order **

here is my OnAccept Event of TcpServer:

procedure TForm2.TcpServerAccept(Sender: TObject;
  ClientSocket: TCustomIpClient);
var
  txt: string;
  PopupAlertThread: TPopupAlertThread;
begin
  // Read the first line from the incoming
  txt:= ClientSocket.Receiveln();
  // create alert popup thread
  PopupAlertThread := TPopupAlertThread.Create(true);

  If txt = 'BUY' then
  begin
    PopupAlertThread.AlertType := 'BUY';
    PopupAlertThread.AlertData := ClientSocket.Receiveln();
    txt:= ClientSocket.Receiveln();
    While txt <> '' do
    begin
      PopupAlertThread.AlertMessage.Append(s);
      txt := ClientSocket.Receiveln();
    end;
  end;
  // Call Resume which will execute and synch/perform the popup
  PopupAlertThread.Resume;
end;

Here is the thread declaration

  // Thread for Alert Popup
  TClientDataThread = class(TThread)
  private
  public
    AlertType, AlertData : String;
    AlertMessage : TStrings;
    procedure threadPopupAlertMessage;
    constructor Create(CreateSuspended: Boolean);
    procedure Execute; override;
    procedure Terminate;
  end;

Here is the thread implementation

//------------- BEGIN My Popup Thread -------------------------------
constructor TPopupAlertThread.Create(CreateSuspended: Boolean);
begin
  inherited Create(CreateSuspended);
  FreeOnTerminate := true;
  AlertMessage := TStringList.Create;
end;

procedure TPopupAlertThread.Terminate;
begin
  AlertMessage.Free;
  inherited;
end;

procedure TPopupAlertThread.Execute;
begin
  Synchronize(threadPopupAlertMessage);
  Self.FreeOnTerminate := True;
  Self.Free;
  If not Self.Terminated then Self.Terminate;
end;

procedure TPopupAlertThread.threadPopupAlertMessage;
begin
  Form2.ShowAlert(AlertType, AlertData, AlertMessage);
end;
//------------- END My Popup Thread ---------------------------

On Mon, 8 Jul 2002 17:36:33 -0700, "Luke Croteau [TriadNet Studios]"

In general I love the Indy components, but I ended up at the TcpServer
components because they are functionally more simple.  The Indy are
bigger and have many functions that I don't need.  I am just sending
transactional messages (i.e. Connect, WriteLn, Disconnect).
BTW...Indy demo using threads had the same error.

On Mon, 08 Jul 2002 13:17:20 -0700, Jason Southwell

I am very surprised that your code is working, besides all the real
processing that is done by your thread
is "synchronized" which makes me wonder why you are using threads in the
first place.

About the access violation:  try removing Self.Free in the thread's Execute
method.

Thinking about  "Self.Free",  isn't that  a very strange statement anyway ?

<Maarten>

Good call Maarten

But thanks for being snippy about it anyway.

--
Jason Southwell
President & CEO
Arcana Technologies

Are you accessing the UI?

--
Chad Z. Hower (a.k.a. Kudzu) - http://www.hower.org/Kudzu/
      "Programming is an art form that fights back"

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