D. J. Bernstein
TCP/IP
ucspi-tcp

The who@ program

who@ prints the list of active users on a remote host.

Interface

     who@ host
who@ connects to TCP port 11 (Systat) on host and prints any data it receives. It removes CR (\015) and converts unprintable characters to a visible format.

If host is not supplied, who@ connects to the local host.

Some computers respond to port 11 with a list of active users. For example, they may be running

     tcpserver -RHl0 0 11 who
using tcpserver.