TCP Keep Alive on idHttpServer (server) and wininet (client)

Question

I have a webserver application developed using idHttpServer. When a client connects do my webserver and, for some unknown reason, got disconnect (not a gracefully disconnect

Answer 1

If you are using an up-to-date Indy 10 release, then you can use the TIdSocketHandle.SetKeepAliveValues() method:

procedure SetKeepAliveValues(const AEnabled: Boolean; const ATimeMS, AInterval: Integer);

For example:

procedure TForm1.IdHTTPServer1Connect(AContext: TIdContext);
begin
  // send a keep-alive every 1 second after
  // 5 seconds of inactivity has been detected
  AContext.Binding.SetKeepAliveValues(True, 5000, 1000);
end;

Note that the ATimeMS and AInterval parameters are only supported on Win2K and later.

Otherwise, use the TIdSocketHandle.SetSockOpt() method directly to enable the TCP/IP SO_KEEPALIVE option manually:

procedure TIdSocketHandle.SetSockOpt(ALevel: TIdSocketOptionLevel; AOptName: TIdSocketOption; AOptVal: Integer);

For example:

procedure TForm1.IdHTTPServer1Connect(AContext: TIdContext);
begin
  AContext.Binding.SetSockOpt(Id_SOL_SOCKET, Id_SO_KEEPALIVE, 1);
end;