indy TCP and activex connect to server issues - delphi

Question

I am trying to transform my delphi project from VCL to ActiveX. I have issues with a client thread. Here is my client thread type:
type
TClientThread = class(TThread)
private
Command: string;
procedure HandleInput;
protected
procedure Execute; override;
end;
And here is the implementation:
procedure TClientThread.HandleInput;
begin
activext.ProcessCommands(Command);
Command := '';
end;
procedure Tactivextest.ProcessCommands(Command: string);
var
Params: array [1 .. 10] of String;
ParamsCount, P: Integer;
PackedParams: TPackedParams;
PStr: String;
IdBytes: TIdBytes;
Ms: TMemoryStream;
ReceiveParams, ReceiveStream: Boolean;
Size: Int64;
begin
Ms := TMemoryStream.Create;
ReceiveParams := False;
ReceiveStream := False;
if Command[1] = '1' then // command with params
begin
Command := Copy(Command, 2, Length(Command));
ReceiveParams := True;
end
else if Command[1] = '2' then // command + memorystream
begin
Command := Copy(Command, 2, Length(Command));
ReceiveStream := True;
Ms.Position := 0;
end
else if Command[1] = '3' then // command with params + memorystream
begin
Command := Copy(Command, 2, Length(Command));
ReceiveParams := True;
ReceiveStream := True;
end;
if ReceiveParams then // params incomming
begin
TCPClient.Socket.ReadBytes(IdBytes, SizeOf(PackedParams), False);
BytesToRaw(IdBytes, PackedParams, SizeOf(PackedParams));
ParamsCount := 0;
repeat
Inc(ParamsCount);
P := Pos(Sep, String(PackedParams.Params));
Params[ParamsCount] := Copy(String(PackedParams.Params), 1, P - 1);
Delete(PackedParams.Params, 1, P + 4);
until PackedParams.Params = '';
end;
if ReceiveStream then // stream incomming
begin
Size := TCPClient.Socket.ReadInt64;
TCPClient.Socket.ReadStream(Ms, Size, False);
Ms.Position := 0;
end;
if Command = 'SIMPLEMESSAGE' then
begin
MessageDlg(Params[1], mtInformation, [mbOk], 0);
end;
if Command = 'INVALIDPASSWORD' then
begin
TCPClient.Disconnect;
MessageDlg('Invalid password!', mtError, [mbOk], 0);
end;
if Command = 'SENDYOURINFO' then // succesfully loged in
begin
UniqueID := StrToInt(Params[1]);
Panel1.Caption := 'connect ' + namewithicon + ')';
PStr := namewithicon + Sep;
SendCommandWithParams(TCPClient, 'TAKEMYINFO', PStr);
end;
if Command = 'DISCONNECTED' then
begin
if TCPClient.Connected then
TCPClient.Disconnect;
end;
if Command = 'TEXTMESSAGE' then
begin
memo1.Lines.Add(Params[1] + ' : ' + Params[2] )
end;
end;
procedure TClientThread.Execute;
begin
inherited;
while not Terminated do
begin
if not activext.TCPClient.Connected then
Terminate
else
begin
if activext.TCPClient.Connected then
Command := activext.TCPClient.Socket.ReadLn('', 5);
if Command <> '' then
Synchronize(HandleInput);
end;
end;
end;
initialization
TActiveFormFactory.Create(
ComServer,
TActiveFormControl,
Tactivextest,
Class_activextest,
0,
'',
OLEMISC_SIMPLEFRAME or OLEMISC_ACTSLIKELABEL,
tmApartment);
end.
And here is how I start the client thread with Indy's TCP OnConnected event:
procedure Tactivextest.TCPClientConnected(Sender: TObject);
begin
ClientThread := TClientThread.Create(True);
ClientThread.Start;
SendCommandWithParams(TCPClient, 'LOGIN', namewithicon + Sep);
end;
And here is how I connect to the server on the Form's OnCreate event:
begin
if not TCPClient.Connected then
begin
TCPClient.Host := 'localhost';
TCPClient.Port := 31000;
try
TCPClient.Connect;
except
on E: Exception do
begin
MessageDlg('Cannot connect to server!', mtInformation, [mbOk], 0);
Application.Terminate;
end;
end;
end
else
begin
SendCommand(TCPClient, 'DISCONNECTED');
if TCPClient.Connected then
TCPClient.Disconnect;
end;
end;
send commands
procedure Tactivextest.SendBuffer(TCPClient: TIdTCPClient; Buffer: TIdBytes;
BufferSize: Cardinal);
begin
if not TCPClient.Connected then
Exit;
TCPClient.Socket.WriteLn('AUDIO');
TCPClient.Socket.Write(BufferSize);
TCPClient.Socket.Write(Buffer, BufferSize);
end;
procedure Tactivextest.SendCommand(TCPClient: TIdTCPClient; Command: string);
begin
if not TCPClient.Connected then
Exit;
TCPClient.Socket.WriteLn(Command);
end;
procedure Tactivextest.SendCommandWithParams(TCPClient: TIdTCPClient;
Command, Params: String);
var
PackedParams: TPackedParams;
begin
if not TCPClient.Connected then
Exit;
TCPClient.Socket.WriteLn('1' + Command);
PackedParams.Params := ShortString(Params);
TCPClient.Socket.Write(RawToBytes(PackedParams, SizeOf(PackedParams)));
end;
procedure Tactivextest.SendStream(TCPClient: TIdTCPClient; Ms: TMemoryStream);
begin
if not TCPClient.Connected then
Exit;
Ms.Position := 0;
with TCPClient.Socket do
begin
Write(Ms.Size);
WriteBufferOpen;
Write(Ms, 0);
WriteBufferClose;
end;
end;
procedure Tactivextest.SendCommandAndStream(TCPClient: TIdTCPClient; Command: String;
Ms: TMemoryStream);
begin
if not TCPClient.Connected then
Exit;
TCPClient.Socket.WriteLn('2' + Command);
Ms.Position := 0;
with TCPClient.Socket do
begin
Write(Ms.Size);
WriteBufferOpen;
Write(Ms, 0);
WriteBufferClose;
end;
end;
procedure Tactivextest.SendCommandWithParamsAndStream(TCPClient: TIdTCPClient;
Command, Params: String; Ms: TMemoryStream);
var
PackedParams: TPackedParams;
begin
if not TCPClient.Connected then
Exit;
SendCommand(TCPClient, '3' + Command);
PackedParams.Params := ShortString(Params);
TCPClient.Socket.Write(RawToBytes(PackedParams, SizeOf(PackedParams)));
Ms.Position := 0;
with TCPClient.Socket do
begin
Write(Ms.Size);
WriteBufferOpen;
Write(Ms, 0);
WriteBufferClose;
end;
end;
I am able to connect to the server, but the client thread cannot be started same as VCL so I am unable to call SendCommands() as I have been disconnected because I cannot use client thread inside ActiveX. I have searched for many days about how to solve, and I cannot find a solution to this problem. I know ActiveX is dead, but this is for education purposes.

Answer 1

It is not possible for TIdTCPClient.OnConnected to not be triggered if Connect() is successful, so the client thread has to be getting created. And if Start() is not raising an exception, then the thread will start running.
However, a major problem with your thread code is that HandleInput() is being run in the context of the main thread via TThread.Synchronize(), which DOES NOT work in a DLL (ActiveX or otherwise) without extra cooperation of the main thread of the hosting EXE. HandleInput() should not be synchronized at all, but then once you fix that, ProcessCommands() is doing things that are not thread-safe (using MessageDlg(), and accessing Panel1 and Memo1 directly), which do need to be synchronized.
So, you need to re-write your thread logic to avoid these pitfalls. Try something more like this:
type
TClientThread = class(TThread)
protected
procedure Execute; override;
end;
procedure TClientThread.Execute;
begin
activext.SendCommandWithParams(activext.TCPClient, 'LOGIN', activext.namewithicon + activext.Sep);
while (not Terminated) and activext.TCPClient.Connected do
begin
Command := activext.TCPClient.Socket.ReadLn('', 5);
if Command <> '' then
activext.ProcessCommands(Command);
end;
end;
type
Tactivextest = class(TActiveForm)
TCPClient: TIdTCPClient;
...
private
...
LineToAdd: string;
procedure UpdatePanel;
procedure AddLineToMemo;
...
end;
procedure Tactivextest.FormCreate(Sender: TObject);
begin
TCPClient.Host := 'localhost';
TCPClient.Port := 31000;
try
TCPClient.Connect;
except
on E: Exception do
begin
MessageBox(0, 'Cannot connect to server!', 'Error', MB_OK);
raise;
end;
end;
end;
// TTimer OnTimer event handler
procedure Tactivextest.Timer1Timer(Sender: TObject);
begin
// needed for TThread.Synchronize() to work in a DLL...
CheckSynchronize;
end;
procedure Tactivextest.TCPClientConnected(Sender: TObject);
begin
ClientThread := TClientThread.Create(False);
end;
procedure Tactivextest.UpdatePanel;
begin
Panel1.Caption := 'connect ' + namewithicon + ')';
end;
procedure Tactivextest.AddLineToMemo;
begin
Memo1.Lines.Add(LineToAdd);
end;
procedure Tactivextest.ProcessCommands(Command: string);
var
Params: array [1 .. 10] of String;
ParamsCount, P: Integer;
PackedParams: TPackedParams;
IdBytes: TIdBytes;
Ms: TMemoryStream;
ReceiveParams, ReceiveStream: Boolean;
Size: Int64;
begin
ReceiveParams := False;
ReceiveStream := False;
Ms := TMemoryStream.Create;
try
case Command[1] of
'1': // command with params
begin
Command := Copy(Command, 2, MaxInt);
ReceiveParams := True;
end;
'2': // command + stream
begin
Command := Copy(Command, 2, MaxInt);
ReceiveStream := True;
end;
'3': // command with params + stream
begin
Command := Copy(Command, 2, MaxInt);
ReceiveParams := True;
ReceiveStream := True;
end;
end;
if ReceiveParams then // params incoming
begin
TCPClient.Socket.ReadBytes(IdBytes, SizeOf(PackedParams), False);
BytesToRaw(IdBytes, PackedParams, SizeOf(PackedParams));
ParamsCount := 0;
repeat
Inc(ParamsCount);
P := Pos(Sep, String(PackedParams.Params));
Params[ParamsCount] := Copy(String(PackedParams.Params), 1, P - 1);
Delete(PackedParams.Params, 1, P + 4);
until (PackedParams.Params = '') or (ParamsCount = 10);
end;
if ReceiveStream then // stream incoming
begin
Size := TCPClient.Socket.ReadInt64;
if Size > 0 then
begin
TCPClient.Socket.ReadStream(Ms, Size, False);
Ms.Position := 0;
end;
end;
if Command = 'SIMPLEMESSAGE' then
begin
MessageBox(0, PChar(Params[1]), 'Message', MB_OK);
end
else if Command = 'INVALIDPASSWORD' then
begin
TCPClient.Disconnect;
MessageBox(0, 'Invalid password!', 'Error', MB_OK);
end
else if Command = 'SENDYOURINFO' then // successfully logged in
begin
UniqueID := StrToInt(Params[1]);
TThread.Synchronize(nil, UpdatePanel);
SendCommandWithParams(TCPClient, 'TAKEMYINFO', namewithicon + Sep);
end
else if Command = 'DISCONNECTED' then
begin
TCPClient.Disconnect;
end
else if Command = 'TEXTMESSAGE' then
begin
LineToAdd := Params[1] + ' : ' + Params[2];
TThread.Synchronize(nil, AddLineToMemo);
end;
finally
Ms.Free;
end;
end;
initialization
TActiveFormFactory.Create(
ComServer,
TActiveFormControl,
Tactivextest,
Class_activextest,
0,
'',
OLEMISC_SIMPLEFRAME or OLEMISC_ACTSLIKELABEL,
tmApartment);
end.