Add support for multiple telnet ports

[DavidRieman]

Our telnet support stack should allow us to register multiple open ports for incoming telnet connections. For this ticket, ensure that the groundwork is present, and it should be possible to track details about the connection based on which port was connected, even before telnet negotiations begin.

(Other features will depend on this ground work, such as connecting with an audible read-out accessibility mode which disables ASCII graphics and decorators that don't "read out" nicely for visually impaired users.)