Calling a REST web service over SSL

I'm struggling to connect to a REST web service that's working only over HTTPS / SSL from my .NET application.

I received the certificate and private key to use as two separate files - a certificate.pem file which contains the certificate, and the webservice.key file which contains the private key. Those are both text files with BASE64 encoded binary data contained in them.

The provider also sent me a PDF showing how to call that web service using CURL and those two files, and that works just fine:

curl.exe -k -v "https://(URL)" --cert certificate.pem --key webservice.key

I need to use the -k option since there seems to be a self-signed certificate somewhere in the hierarchy of certs. Without this option, the call fails.

In order to call this web service from a .NET application (a console app for now), I used OpenSSL (on Windows) to combine these two files into a *.pfx file using this command:

openssl pkcs12 -export -out webservice.pfx -in certificate.pem -inkey webservice.key 

This seems to have worked, too - no errors were reported, the file was created and is about 3K in size and it's a totally binary file.

Now, I tried to call that web service from my .NET code something like this:

try
{
    // use the SSL protocol (instead of TLS)
    ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3;

    // ignore any certificate complaints
    ServicePointManager.ServerCertificateValidationCallback += (sender, certificate, chain, sslPolicyErrors) => { return true; };

    // create HTTP web request with proper content type
    HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
    request.ContentType = "application/xml;charset=UTF8";

    // grab the PFX as a X.509 certificate from disk
    string certFileName = Path.Combine(certPath, "webservice.pfx");

    // load the X.509 certificate and add to the web request
    X509Certificate cert = new X509Certificate(certFileName, "(top-secret password)");
    request.ClientCertificates.Add(cert);
    request.PreAuthenticate = true;

    // call the web service and get response
    WebResponse response = request.GetResponse();

    Stream responseStream = response.GetResponseStream();
}
catch (Exception exc)
{
    // log and print out error
}

However, I can try whatever I like (fiddling around with various settings, on the ServicePointManager and the HttpWebRequest, but I just keep getting these errors:

WebException: The underlying connection was closed: An unexpected error occurred on a send.

IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.

SocketException: An existing connection was forcibly closed by the remote host

and no response - even though communicating with the service with CURL has worked just fine.....

What am I missing?? I'm a bit puzzled and mystified by all those certificates, private keys, service point manager options and so on - just waaaaay too many knob and switches to turn, set or turn off - what are the RIGHT settings here??

Update:

If I use

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls;

then the error just simply is:

WebException: The request was aborted: Could not create SSL/TLS secure channel.

S O L U T I O N :

In the end, with looking at the output from curl and a lot of help from @Alexandru and @JurajMajer, I was able to get this to work with this code:

try
{
    // use the TLS protocol 
    ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls;

    // create HTTP web request with proper content type
    HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
    request.ContentType = "application/xml;charset=UTF8";

    // grab the PFX as a X.509 certificate from disk
    string certFileName = Path.Combine(certPath, "webservice.pfx");

    // load the X.509 certificate and add to the web request
    X509Certificate2 cert = new X509Certificate2(certFileName, "(top-secret password)");
    request.ClientCertificates.Add(cert);
    request.PreAuthenticate = true;

    // call the web service and get response
    WebResponse response = request.GetResponse();

    Stream responseStream = response.GetResponseStream();

    string xmlContents = new StreamReader(responseStream).ReadToEnd();
}
catch (Exception exc)
{
    // log and print out error
}