CL-USER> (ql:quickload :usocket)
To load "usocket":
  Load 1 ASDF system:
    usocket
; Loading "usocket"

(:USOCKET)
CL-USER> (use-package :usocket)
T
CL-USER> (defvar *server* (socket-listen "127.0.0.1" 65432))
*SERVER*
CL-USER> (defvar *client-1* (socket-connect "127.0.0.1" 65432))
*CLIENT-1*
CL-USER> (defvar *client-2* (socket-accept (wait-for-input *server*)))
*CLIENT-2*
CL-USER> (print "hello world!" (socket-stream *client-1*))
"hello world!"
CL-USER> (finish-output (socket-stream *client-1*))
NIL
CL-USER> (read-line (socket-stream *client-2*))
"\"hello world!\" "
NIL