Thanks for your answer.
I looked at the WS Administrator Console and found that there are two ports defined for my application server already -- 9085 for HTTP and 9444 for HTTPS. You are right. I saw the "Enable SSL" check box is selected in the second port.
After configuring a keystore file for IBM HTTP Server and enabling SSL for the first port, I could connect to <a href="https://<my_server_name rel="nofollow">:9085/<my_web_service_url>" target="_blank">
https://<my_server_name>:9085/<my_web_service_url>
However, my problem is that I cannot connect to <a href="https://<my_server_name rel="nofollow">:9444/<my_web_service_url>." target="_blank">
https://<my_server_name>:9444/<my_web_service_url>. WS logs an error message saying "Servlet Request Processor Exception: Virtual Host/WebGroup Not Found : The host <my_server_name> on port 9444 has not been defined"
Could you pls tell me why the default SSL port does not work?