Disconnect unknow connections at TIdTcpServer OnConnect - delphi

Question

I'm having a problem. I created a TIdTCPServer but I need to prevent false/unknown connections.
I tried this:
procedure Wait(millisecs: Integer);
var
tick: dword;
AnEvent: THandle;
begin
AnEvent := CreateEvent(nil, False, False, nil);
try
tick := GetTickCount + dword(millisecs);
while (millisecs > 0) and (MsgWaitForMultipleObjects(1, AnEvent, False, millisecs, QS_ALLINPUT) <> WAIT_TIMEOUT) do begin
Application.ProcessMessages;
if Application.Terminated then Exit;
millisecs := tick - GetTickcount;
end;
finally
CloseHandle(AnEvent);
end;
end;
procedure CheckCon(Con: Pointer);
begin
Wait(5000);
if TClient(Con).HWID = '' then TClient(Con).Connection.Disconnect;
EndThread(0);
end;
constructor TClient.Create(AConnection: TIdTCPConnection; AYarn: TIdYarn; AList: TIdContextThreadList = nil);
var
ThreadId : Cardinal;
begin
inherited Create(AConnection, AYarn, AList);
FCriticalSection := TCriticalSection.Create;
Queue := TIdThreadSafeStringList.Create;
BeginThread(nil, 0, #CheckCon, Self, 0, ThreadId);
end;
OnConnect event code:
procedure TForm1.IdTCPServer1Connect(AContext: TIdContext);
var
Conexao : TClient;
Retorno : TArray<String>;
Query : TFDQuery;
Libera : Boolean;
IPEX : Boolean;
begin
Libera := True;
IPEX := True;
Conexao := TClient(AContext);
Retorno := AContext.Connection.IOHandler.ReadLn.Split(['#']);
if Length(Retorno) = 0 then
begin
AContext.Connection.Disconnect;
Exit;
end;
Conexao.IP := AContext.Connection.Socket.Binding.PeerIP;
Conexao.HWID := Retorno[1];
Conexao.Connected := Now;
Conexao.Ping := Ticks;
ClientStateUpdated(Conexao, RetornaTraducao(40));
TThread.Queue(nil,
procedure
begin
Memo2.Lines.Add(Format(RetornaTraducao(36), [TimeToStr(Now), Conexao.IP, Conexao.HWID]));
end);
end;
If I test creating a low number of unknown clients, it works good, but if I flood it with MANY connections, the application crashes. I need something like this to prevent unknown connections in my TIdTCPServer.
I tried calling
Memo2.Lines.Add(Format('[%s]', [AContext.Connection.IOHandler.ReadLn]));
in IdTCPServer1Connect to determine if the connection was my application, but if the client only connects and doesn't send anything, the line doesn't execute.

Answer 1

Starting a worker thread inside of TClient's constructor is completely unnecessary (the TClient object is already run in a thread created by the server). You can simply set a 5 second timeout on the ReadLn() call itself and be done with it.
Also, TIdTCPServer is a multi-threaded component, its events are fired in the context of worker threads, so access to UI controls like Memo2 MUST by synchronized with the UI thread or else bad things happen.
Try something more like this:
constructor TClient.Create(AConnection: TIdTCPConnection; AYarn: TIdYarn; AList: TIdContextThreadList = nil);
begin
inherited Create(AConnection, AYarn, AList);
FCriticalSection := TCriticalSection.Create;
Queue := TIdThreadSafeStringList.Create;
end;
...
// code adapted from my reply to your previous question:
//
// https://stackoverflow.com/a/58479489/65863
//
// tweak as needed...
//
procedure TForm1.ClientStateUpdated(Client: TClient; const Msg: string);
var
IP, HWID: string;
begin
IP := Client.IP;
HWID := Client.HWID;
TThread.Queue(nil,
procedure
begin
Memo2.Lines.Add(Format(RetornaTraducao(36), [TimeToStr(Now), IP, HWID, Msg]));
end
);
end;
procedure TForm1.IdTCPServer1Connect(AContext: TIdContext);
var
Conexao : TClient;
Retorno : TArray<String>;
begin
Conexao := TClient(AContext);
Retorno := AContext.Connection.IOHandler.ReadLn(LF, 5000).Split(['#']);
if (Length(Retorno) < 2) or (Retorno[1] = '') then
begin
AContext.Connection.Disconnect;
Exit;
end;
Conexao.IP := AContext.Binding.PeerIP;
Conexao.HWID := Retorno[1];
Conexao.Connected := Now;
Conexao.Ping := Ticks;
ClientStateUpdated(Conexao, RetornaTraducao(40){'connect'});
end;
procedure TForm1.IdTCPServer1Disconnect(AContext: TIdContext);
var
Conexao : TClient;
begin
Conexao := TClient(AContext);
if Conexao.Connected <> 0 then
ClientStateUpdated(Conexao, RetornaTraducao(...){'disconnect'});
end;