Check the server's firewall settings to make sure the port is not blocked from being accessed. You can try to temporarily turn off the firewall or add the corresponding port exception rule.
Network connection problem
Make sure the connection between the server and the public network is normal. You can try to use other network environment or replace the network equipment to solve the problem.
Port occupation problem
Make sure the port is not already occupied by other programs. You can use the netstat command to check the port occupation and close the relevant program or change the port number.
Program configuration problems
Make sure that the program's configuration file is correctly set up with the port's listening and access rights and other related parameters. You can check the program's log file to determine if there is a configuration problem.
Hardware failure problem
If there is no problem with the above points, then there may be a hardware failure on the site server itself, which requires further inspection and repair.