Nginx secure port 443 is not opened/ connection refuse

Question

I have installed nginx on my ubuntu VM. There I want Nginx to listen 443 port. My configurations are as follows.

server {
    listen 443;
    server_name wso2test.com;

    ssl on;
    ssl_certificate /etc/nginx/ssl/server.crt;
    ssl_certificate_key /etc/nginx/ssl/server.key;

    #with portOffset 0 running AS
    location /appserver/ {
        proxy_pass https://10.100.1.173:9443/;
    }

}

Then I tried and could not connect to this listening port from other machine. Then I telnet to nginx machine 443 port. It gives me connection refused output. But telnet to 80 port is connecting. what is the reason for this ?