Telnet through a serial terminal server

serialtelnet

I have a Perle IOLAN device like this, and one configuration option is for a serial terminal.

The corresponding configuration screen.

As you can see, one option is to configure the terminal to connect to a Telnet server. Can somebody explain how it is possible for the telnet application protocol to be transported over a serial link (from the terminal to the IOLAN)? My understanding was that Telnet is exclusive to TCP.

A follow up question is how to configure a Linux host as a terminal for the purposes of connecting to an IOLAN (i.e. emulate a terminal).

Best Answer

how it is possible for the telnet application protocol to be transported over a serial link

That isn't what happens. You use telnet to connect to the terminal server. The 'telnet' session does not get transmitted over serial. Instead, when you connect to the terminal server via telnet a process is started within that session that connects to the serial device.

It is more or less the same as what would happen if you used SSH to connect to a linux box, then use GNU screen to connect to some serial device that was connected to that remote system.

Linux host as a terminal for the purposes of connecting to an IOLAN

There are lots of guides about running a Linux box with a serial console. It usually invokes configuring your bootloader (grub) to listen on the serial port, and configuring a getty via in your init daemon to listen on the serial port.

If the device you are connecting to is already configured to work on a serial port (like console ports for network equipment) then you probably don't have to do anything.