COMSERV is a program that runs on Unix (developed on FreeBSD) that allows you to talk to a network terminal server such as a Xyplex MAXserver 1600. The handy thing about this program is that the client side of the connection does not need to know anything about how to talk to the terminal server. COMSERV handles the connection details. Thus, you can use existing programs like tip to talk to devices attached to your network terminal server without modification.
Also, you can use COMSERV to turn your Unix computer itself into a terminal server and serve up its own local serial ports over the network for remote systems to access. This is handy if you have several systems lying around and you want to utilize devices attached to their serial ports.