DOKK / manpages / debian 12 / ucspi-tcp / who@.1.en
who@(1) General Commands Manual who@(1)

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

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.

tcpserver(1), tcprules(1), tcprulescheck(1), argv0(1), fixcrio(1), recordio(1), rblsmtpd(1), tcpclient(1), date@(1), finger@(1), http@(1), tcpcat(1), mconnect(1), tcp-environ(5)

http://cr.yp.to/ucspi-tcp.html