Can not use all listening port with domain that has ssl

Hey, I have a Linux VPS that pointed a domain to its static IP and use Cloudflare flexible SSL, with the default port (80) my domain is ok, opens and also https is ok, but with another port like 81 I can not open my another site, below is my condition:

sample.com --site ok, SSL ok
staticIP:80 --site ok, SSL not ok
sample.com:81 --site not ok, SSL not ok
staticIP:81 --site ok, SSL not ok

I need to open both sites with a domain name in these two ports(80,81) and https would be ok for both,
what is my wrong? and what is the best solution?

thanks for your help,