You can use write command.
As @MelBurslan commented, if write permission is off, first execute:
$ mesg y
From man mesg
OPTIONS
y Allow write access to your terminal.
Usage of write:
$ write username tty
e.g. Send ls output to other terminal.
$ w
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
user :0 :0 08:15 ?xdm? 7:37 0.25s init --user
user pts/0 :0 08:19 1.00s 0.09s 0.01s w
user pts/12 :0 08:50 54.00s 0.03s 0.03s bash
$ ls | write username pts/12