Port 50000 is used on these devices as a potential point of connection to the device via a method which we refer to as pmodem or pseudo modem. This connection consists of a Raw TCP socket which is mapped to the first available port which is configured for use in pseudo modem mode. If no ports are configured for pmodem operation, then the connection will terminate after any data is attempted to be sent to the socket. If a socket was configured for pmodem operation then connecting on the socket 50000 would provide a Raw TCP connection to the attached serial device that was attached to that port (or to the first available port so configured). Configuring pmodem mode on a port also creates a direct raw socket connection (i.e. 50001, 50002, …) for the port itself so this does not create a unique method of access, simply a way to treat the ports so configured as a group.
There is no way in the device configuration to disable port 50000 but as noted above it has no security impact on the device beyond the fact that it will show up on some security scans, as it only provides connectivity when serial ports on the device are specifically configured to work with it.
Aug 08, 2017