Exception: Unrecognized SSL message, plaintext connection?

Hi all,

This is my first time I use SopaUI (version 4.5.1) and I try to use it for testing a client WS.
My client simply sends a request to a local server (http://localhost:8070/test) I set up via SoapUI.

These were my steps:
1. I created server and client certificates as below:

keytool -genkey -alias server -keyalg RSA -validity 3650 -keystore c:\server.keystore -storepass abcd1234 -keypass abcd1234
keytool -export -alias server -keystore c:\server.keystore -storepass abcd1234 -file c:\server.cer

keytool -genkey -alias client -keyalg RSA -validity 3650 -keystore c:\client.keystore -storepass abcd1234 -keypass abcd1234
keytool -genkey -alias client -keyalg RSA -storetype PKCS12 -keystore c:\client.p12 -storepass abcd1234 -keypass abcd1234
keytool -export -alias client -keystore c:\client.p12 -storetype PKCS12 -storepass abcd1234 -file c:\client.cer
keytool -import -alias server -keystore c:\client.keystore -storepass abcd1234 -file c:\server.cer
keytool -import -alias client -keystore c:\server.keystore -storepass abcd1234 -file c:\client.cer

2. In Soap UI I set up both certificates in File->Preferences->SSL Settings page (please see the attached file 'SSL settings.jpg').

3. I created a SoapUI project via WSDL and I create a SOAP12 Binding Mock Service to simulate server response and started it

4. If I run an HTTP request the execution will be ok (please see attached file 'http request.jpg), while I will get the error 'Error getting response; Unrecognized SSL message, plaintext connection?' if I try to send an HTTPS request (please see attached file 'https request.jpg').

I also tried to add both certificates in Project View -> WS-Security Configurations -> Keystores TAB but the result was the same.
I also tried to send both requests from a Spring test project, but I got the same result.
Then, I have supposed there is something wrong on server side.
May someone help me in find out what is wrong in my settings?

Thank you so much.