Something I commonly see is people who believe a port is blocked by a firewall appliance (i.e. iptables, router/switch level, etc) because it shows closed on something like https://www.yougetsignal.com/tools/open-ports/
But, in all reality, many times it is because there is nothing listening on the port in the question, and for the correct protocol (IPv4/IPv6).
You can use something like `netstat` to check this, i.e. `netstat -nap | grep 8000`. Perhaps you can share the output of that command?