从 Delphi 10.3 中的 TWebBrowser OnNavigateError 中提取 StatusCode

Question

I'm trying to get the HTTP response code in an OnNavigateError event of a TWebBrowser. The StatusCode passed to me is always -2146697211 when it should be 404. What am I missing? I'm using Delphi 10.3.

Answer 1

• TWebBrowser uses Microsoft's Internet Explorer, so information about the NavigateError event can be found online .
• The explanation of the StatusCode parameter links to "NavigateError Event Status Codes" - there you see your typical 3-digit HTTP status codes, but also additional ones. Your decimal value of -2146697211 is $800C0005 in hexadecimal - both match the INET_E_RESOURCE_NOT_FOUND constant, which again links to another page :
• It means "The server or proxy was not found."

Why is this a separate error code and not a HTTP one? Because it happens before HTTP is performed: looking up the IP address to a hostname has failed - nobody knows which IP address the hostname you tried to browse to has. That's what the Domain Name System (DNS) is for. Not being able to get in contact with a server is a different thing than being able and getting a response. HTTP 404 is a reponse. But since you don't even got a response, hence you cannot get a HTTP status code.

---

Long story short: host not found (instead of "HTTP 404" = host found, but not the page you're looking for ). Try it with an address/a hostname that can be actually resolved.