8443
Alternate HTTPS port for secondary services
HTTPS Alternate
What is port 8443?
Port 8443 is used as an alternate HTTPS port when port 443 is unavailable or is already in use by another service. It is very common in Apache Tomcat (HTTPS connector), the Plesk control panel, and various enterprise Java applications. Kubernetes ingress controllers also frequently use it for HTTPS traffic.
Quick checks
$
nc -zv example.com 8443
$
nmap -p 8443 example.com
$
telnet example.com 8443