THttpClient is not closing connection in Delphi

Question

My software includes the function below for posting to URL. I'm using Sysinternals TCPView to see the connection. The connection is not closing after posting to URL. How should I change the code for immediate connection close?

function PostURL(const AURL: string; Parameters: TStrings): string;
var
  HttpClient: THttpClient;
  HttpResponse: IHttpResponse;
begin
  HttpClient := THTTPClient.Create;
  try
    HttpClient.ConnectionTimeout:=3000;
    HttpClient.ResponseTimeout:=3000;
    HttpResponse := HttpClient.Post(AURL, Parameters, nil, TEncoding.UTF8);
    Result := HttpResponse.ContentAsString();
  finally
    HttpClient.Free;
  end;
end;

I do not find a Disconnect method. If I were you, I would use a well established library like Indy (use TIdHttp)... Tokyo comes with Indy components so you have it already. — whosrdaddy, Jan 18 '18 at 12:28
Sure it can ;) Best is to distribute openssl dlls with your application. — whosrdaddy, Jan 18 '18 at 13:00
I would expect `THTTPClient` to disconnect when it is destroyed. If it is not, file a bug report with Embarcadero — Remy Lebeau, Jan 18 '18 at 14:58
`"Indy can not connect to https web sites on some computers."` That is nonsense. If you have a problem implementing that, don't just give up - try to understand what you're doing wrong, and address it. Indy is perfectly capable of HTTPS. You just have to set it up as desired. — Jerry Dodge, Jan 18 '18 at 16:42
@JerryDodge and as whosrdaddy said, ensure the libraries are distributed with the app. — Gerry Coll, Jan 19 '18 at 01:56
I dont prefer distributing the openssl libraries. I stick to THttpClient. — Xel Naga, Jan 19 '18 at 12:05

score 5 · Answer 1 · answered Jan 18 '18 at 20:18

This is a feature of WinHttp, it keeps TCP connections alive for some time to reuse them faster, you can disable it by disabling this option in request.

OptionValue := WINHTTP_DISABLE_KEEP_ALIVE;
WinHttpSetOption(RequestHandle, WINHTTP_OPTION_DISABLE_FEATURE, @OptionValue, sizeof(OptionValue));

But there is no easy way to set this option in Delphi THttpClient, to do it you'll have to copy System.Net.HttpClient.Win.pas and System.Net.HttpClient.pas to your project and modify System.Net.HttpClient.Win.pas to add this code

score 2 · Accepted Answer · answered Apr 29 '20 at 00:30

2

what about the following

 HttpClient.SetRequestHeader('Connection', 'close');

answered Apr 29 '20 at 00:30

Justin

927
11
24

Error: Undeclared identifier: 'SetRequestHeader' – Xel Naga Apr 29 '20 at 05:17
1

Hooray! This one works! HttpClient.CustomHeaders['Connection']:='close'; – Xel Naga Apr 29 '20 at 05:23
cool, yes I was using winhttp hence the syntax difference but you figured out :) – Justin Apr 29 '20 at 12:31

THttpClient is not closing connection in Delphi

2 Answers2