Perforce stopped connecting

I ran up a perforce dev servers for couple users for a year and bit with no problems, then they reported it refuses connection to their clients last week. I logged into the server and tried "p4 info", and get

Perforce client error:

    Connect to server failed; check $P4PORT.

    connect: 127.0.0.1:1666: Connection refused

and when tried "p4 -p servername:port" i get similar return with servers IP.

It's hard to know for sure without more information, is the server running on Windows or Linux? What method did you use to install it?

Its possible that the server was setup with a secure ssl connection so it is refusing the connection request without it.
Try p4 -p ssl:servername:port and see if adding the ssl at the beginning makes a difference.

It's also worth checking if the server is running. It's possible that something went wrong with the install or the VM itself and the server isn't running. On Linux you can usually check that with systemctl (the name of the service might vary based on how you installed it) and on Windows you can check the Process Monitor and look for the Perforce service.

Basically solved this with help of a coworker who is more experienced in Linux. Turns out he used p4dctl to provide more verbose in the error, where it turned out to be a permission issue with database file, state.xu. I guess the upgrade changed the permission of the file. He used this command to load the correct environment and user etc..

p4dctl exec -t p4d perforce -- -xu
Perforce server error:
        chmod: state.xu: Operation not permitted
p4dctl error:
        'perforce' p4d: '/opt/perforce/sbin/p4d -xu' exited with status 255.

After locating the file(s), cleaning up the extra but also changing permissions, he ran the command again and the upgrades were applied at server startup. then he restarted the service and application started running again.

systemctl restart perforce-p4dctl.service