Indy, TidNotify and closing TidTCPServer - connection

Question

I have a TidTCPServer which use database manipulating inside onExcecute event (by using TidNotify). Everything works very good instead of possibility closing application.
During closing application I do not know whether everything Notify instances finished their work or not and usually I get Runtime Error 216 (I think I close database before "notify" work end).
Is any way to check - are there waiting old Notify posts or not to be sure I can close application.
Other question is how to protect TidTCPServer from accepting new connection during closing server process.
I use code like below but I obtain the error still.
type
TShutdownThread = class(TThread)
protected
procedure Execute; override;
end;
procedure TShutdownThread.Execute;
begin
IdTCPServer.Active := false;
end;
//closing...
if IdTCPServer.Active then
begin
with TShutdownThread.Create(false) do
try
WaitFor; // internally processes sync requests...
finally
Free;
end;
end;

Answer 1

Is any way to check - are there
waiting old Notify posts or not to be sure I can close
application.
TIdNotify is asynchronous, it posts requests to the main thread message queue for later execution. It is possible that pending requests are still in the queue after TShutdownThread.WaitFor() has exited. You can call the RTL's CheckSynchronize() function to process any remaining requests, eg:
if IdTCPServer.Active then
begin
with TShutdownThread.Create(false) do
try
WaitFor;
finally
Free;
end;
CheckSynchronize;
end;
how to protect TidTCPServer from accepting new connection during closing server process.
While TIdTCPServer is being deactivated, it closes its listening port(s) for you. However, there is a very small window of opportunity when new clients could be accepted before the server closes the port(s). The server will close those connections as part of its shutdown, but if you do not want the OnExecute event to be called for those connections then you can set a flag somewhere in your code before deactivating the server, then check for that flag in the OnConnect event, and if it is set then disconnect the client immediately, eg:
var
ShuttingDown: boolean = False;
procedure TForm1.IdTCPServer1Connect(AContext: TIdContext);
begin
if ShuttingDown then
begin
AContext.Connection.Disconnect;
Exit;
end;
...
end;
...
if IdTCPServer.Active then
begin
ShuttingDown := True;
try
with TShutdownThread.Create(false) do
try
WaitFor;
finally
Free;
end;
CheckSynchronize;
finally
ShuttingDown := False;
end;
end;