P.S. про 2000, 4000 и 6000 порты.
Support Reverse Telnet Connections
In addition to initiating connections, the access server can receive incoming connections on asynchronous lines. This capability allows you to attach serial printers, modems, and other shared peripherals to the access server and drive them remotely from other systems. The access server supports reverse Telnet connections.
The specific TCP port or socket to which you attach the peripheral device determines the type of service the access server provides on that line. When you attach the serial lines of a computer system or a data terminal switch to a line of the access server, the access server acts as a network front end for a host that does not support the TCP/IP protocols. This arrangement is sometimes called front-ending or reverse connection mode.
To connect an asynchronous line on an access server, the remote host or terminal must specify a particular TCP port on the access server. If Telnet protocols are required, that port is 2000 (decimal) plus the decimal value of the line number.
If a raw TCP stream is required, the port is 4000 (decimal) plus the decimal line number. The raw TCP stream is usually the required mode for sending data to a printer.
The Telnet protocol requires that carriage return characters be translated into carriage return and linefeed character pairs. You can turn this translation off by specifying the Telnet binary mode option. To specify this option, connect to port 6000 (decimal) plus the decimal line number.
P.P.S. Сейчас пытаюсь выяснить что за 9000 у меня открыты...
Хотя по telnet 9001 открывает и сразу закрывает.