Check to see if Plex can be seen from the outside first, by using a service such as GRC ShieldsUp or another online port scanner.
For ShieldsUp, enter the tool using: https://www.grc.com/shieldsup. Click Proceed (it should show your Public IPv4 address on this page). In the box at the center of the following page, type "32400" then select "User Specified Custom Port Probe." The TruStealth Analysis page should give a "Failed" message, indicating that port 32400 is wide open.
For this to pass, the following must be true:
- Plex must be running
- Plex must be set to use Port 32400 (disable automatic port selection / UPnP functionality in Plex's Remote Access menu)
- Your Port Forwarding rules must be correct. For example, the rule must have TCP Any (Source Port) --> Port 32400 (Destination Port). UDP is not used by Plex.
- The forwarded IP address in the port forward rule must match. For example, if the rule is set to forward port 32400 to 192.168.1.100, Plex is expected to always be at that IP address on your LAN. For this to remain true, I recommend either setting up a DHCP Reservation in your router, OR assigning your server machine an IP address outside of the DHCP range with a Static IP.
- The firewall on your server must allow inbound traffic to port 32400 from the Internet. Even if the application is allowed in the firewall, other settings can still prevent your allow rule from taking effect as Deny rules typically take precedence. For example, Windows Firewall under the Advanced Security pane can allow services to be accessible from computers on the same network (LAN), but can deny/filter traffic from the Internet.
- Your router's firewall must not be set too high. Setting it too high will cause port forwarding rules to be disabled.
- UPnP may be interfering with manual port forward rules. Disable UPnP support in Plex OR the router so rules are not overridden.
