I recently spent a weekend revisiting Telnet, not as a sysadmin, but as a Lisp programmer. Why? Because stripping away TLS, JSON, and REST frameworks reveals something beautiful:

Telnet (and its modern descendant, the raw TCP socket) is minimalist. You open a port, you read bytes, you write bytes. That's it.

(defun start-tlen-server (&optional (port 2323)) "Start a Telnet-like server on PORT." (let ((listener (usocket:socket-listen "0.0.0.0" port))) (format t "~&TLEN Server listening on port ~A~%" port) (loop (let ((client-stream (usocket:socket-stream (usocket:socket-accept listener)))) (format t "~&New connection from ~A~%" client-stream) ;; Handle one client, then close (simple for demo) (handler-case (handle-client client-stream) (error (e) (format t "Error: ~A~%" e))) (close client-stream)))))

Next time you need to debug an SMTP server or test a custom TCP service, skip nc (netcat) for an hour. Fire up a Lisp REPL, open a socket, and talk to the machine directly. You'll never look at curl the same way again. If you landed here searching for "Lisp CLOS" (Common Lisp Object System) or "Lisp TCO" (Tail Call Optimization), drop a comment below. I've got drafts on both. But if you really meant tlen as some obscure library... well, now you know how to roll your own. Happy hacking, parentheses and all.