What can be done to get SecurityProtocol working, I'm getting "The SSL connection could not be established"? - powershell

Question

I'm building an ASP.NET Core 3.0 web application, that gets deployed using Octopus. This is all working just fine. We're going live soon, so I've been hardening the servers, by removing insecure protocols etc. using IISCrypto. Only one left is Tls 1.2.
Now all of a sudden I can't do a HttpWebRequest to my deployed web application from a .NET Core command line tool I have written for commissioning the application. I'm getting this error in the logs:
System.Net.WebException: The SSL connection could not be established, see inner exception. Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host..
---> System.Net.Http.HttpRequestException: The SSL connection could not be established, see inner exception.
---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host..
---> System.Net.Sockets.SocketException (10054): An existing connection was forcibly closed by the remote host.
So I tried using some of the suggestions found on SO:
System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
But this doesn't change anything. It's like this line gets ignored.
The code that fails:
HttpWebRequest http = (HttpWebRequest)WebRequest.Create(new Uri(url));
http.Accept = "application/json";
http.ContentType = "application/json";
http.Method = method;
if (String.IsNullOrWhiteSpace(token) == false) {
http.Headers.Add("Authorization", $"Bearer {token}");
}
if (String.IsNullOrWhiteSpace(data) == false) {
UTF8Encoding encoding = new UTF8Encoding();
Byte[] bytes = encoding.GetBytes(data);
Stream newStream = http.GetRequestStream();
newStream.Write(bytes, 0, bytes.Length);
newStream.Close();
}
try {
WebResponse response = http.GetResponse();
Stream stream = response.GetResponseStream();
StreamReader sr = new StreamReader(stream);
return sr.ReadToEnd();
}
catch (Exception ex) {
logger.Error(ex, $"{method} on {relativeUrl} failed");
Console.WriteLine(ex.Message);
}
Just to try something else, I did a small test from Powershell, and I ended up getting a similar error message. Then I added the security protocol line to the script, and it works:
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
Invoke-WebRequest -UseBasicParsing https://mysite/app/authenticate -ContentType "application/json" -Method POST -Body (#{"emailAddress"="somemail#address"; "password"="somepassword"}|ConvertTo-Json)
Any ideas as to why this isn't working with .NET Core ?

Answer 1

This actually turned out to be "wrong server" issue. For some reason my request ended up on the wrong server, and this apparently is the reply/error you get, when you request something on a server that does not have the requested site hosted.