Delphi Indy HTTPS web server errors (EOF was observed that violates the protocol)

Question

I am trying to add HTTPS support to an existing web server written in Delphi XE7 using Indy. I have written a simple application which just returns a date/time stamp on each HTTPS request.

I added handlers to the OnCommandGet and OnException events:

procedure TForm13.HTTPServerCommandGet(AContext: TIdContext; ARequestInfo: TIdHTTPRequestInfo; AResponseInfo: TIdHTTPResponseInfo);
begin
  AResponseInfo.ContentText := DateTimeToStr(Now());
  AResponseInfo.ContentEncoding := 'utf8';

  Log('Request: %s', [ARequestInfo.URI]);
end;

procedure TForm13.HTTPServerException(AContext: TIdContext; AException: Exception);
begin
  Log('Exception raised %s:%s', [AException.ClassName, AException.Message]);
end;

Bindings code:

  with HTTPServer do
   begin
     with Bindings.Add() do
      begin
        IP := '0.0.0.0';
        Port := 443;
      end;

     Active := true;
   end;

When I perfrom a request from a browser, in most cases I get this:

12.03.2019 0:50:29  Exception raised EIdConnClosedGracefully:Connection Closed Gracefully.
12.03.2019 0:50:29  Exception raised EIdConnClosedGracefully:Connection Closed Gracefully.
12.03.2019 0:50:30  Request: /
12.03.2019 0:50:30  Exception raised EIdConnClosedGracefully:Connection Closed Gracefully.
12.03.2019 0:50:30  Request: /favicon.ico
12.03.2019 0:51:00  Exception raised EIdSocketError:Socket Error # 10060    Connection timed out.

It serves the request and the browser shows the timestamp. But why does a graceful connection close raise an exception?

What bothers me more is that sometimes after 30 seconds after the last request, I get another exception, like this:

12.03.2019 1:44:53  Exception raised EIdConnClosedGracefully:Connection Closed Gracefully.
12.03.2019 1:44:53  Exception raised EIdConnClosedGracefully:Connection Closed Gracefully.
12.03.2019 1:44:53  Request: /
12.03.2019 1:44:54  Exception raised EIdConnClosedGracefully:Connection Closed Gracefully.
12.03.2019 1:44:54  Request: /favicon.ico
12.03.2019 1:45:24  Exception raised EIdOSSLAcceptError:Error accepting connection with SSL. EOF was observed that violates the protocol

It happens randomly, sometimes it is a timeout, sometimes this one. This looks wrong for me. Any ideas why this happens?

PS: In Delphi 10.3 it happens the same way as in Delphi XE7, so probably all Indy versions are affected.

On a side note, utf8 is not a valid value for the AResponseInfo.ContentEncoding property. If you want the text to be UTF-8 encoded, you need to set the AResponseInfo.CharSet property instead. — Remy Lebeau
You did not show the code that sets up the server's Bindings collection. Are you making the server listen on port 80 or 443? Do you have an OnQuerySSLPort event handler assigned? The symptoms you describe are caused by the client disconnecting on its end. The EIdConnClosedGracefully is perfectly normal, just ignore it. It means the client disconnected in between requests. The EOF error means the client disconnected in the middle of the SSL/TLS handshake. — Remy Lebeau
I have added bindings code to the post, but I am sure there is nothing special in it. I also tryed to add OnQuerySSLPort (always returning true), it does not change anything. — Дмитрий Алферьев
how exactly have your configured the SSLIOHandler that you have assigned to the server? — Remy Lebeau
I have tried different variants in SSLOptions: Mode: sslmServer or sslmUnassigned, SSLVersions: different sets, CertFile, KeyFile and RootCertFile are all assigned to a same file with self-created certificate. — Дмитрий Алферьев

Дмитрий Алферьев Дмитрий Алферьев · Accepted Answer · 2019-04-29T15:07:36

Finally found that all this strange errors appear only in case of self-generated certificate which is not installed on client device.

Delphi Indy HTTPS web server errors (EOF was observed that violates the protocol)

1 Answers