Issue Description
The server cannot be remotely connected through SSH after the SSH port is modified.
Possible Reasons
The SSH port is 22 by default. If the user changes the SSH port to another port (for example, 10001), but the iptables rule on the server is not modified, the request from port 10001 is denied.
Solutions
Allow access to port 10001 in iptables
iptables -A INPUT -p tcp --dport 10001 -j ACCEPT