(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)))))
Note: "Tlen" is not a standard term in mainstream Lisp literature (Clojure, Common Lisp, Racket, etc.). It is most likely a typo or autocorrect error. Based on common search patterns, I have assumed you meant one of three things: (Common Lisp Object System), "TCO" (Tail Call Optimization), or "TELNET" (network protocols). lisp tlen
;;; tlen.lisp - A minimalist Telnet echo server (require :usocket) ; A portable socket library (defun handle-client (stream) "Echo back whatever the client sends, but shout it in uppercase." (loop :for line = (read-line stream nil) :while line :do (write-line (string-upcase line) stream) (force-output stream))) ;;; tlen
If you meant a specific library or different term, just let me know and I will rewrite the post for you. Remember Telnet? 15 lines of Lisp, and you have a protocol server
That's it. 15 lines of Lisp, and you have a protocol server. You might think: "A loop that reads and writes? Python can do that."
If you came of age in the modern cloud era (Post-2010), Telnet is that "insecure thing" you disable on routers. But for those of us who cut our teeth on BBSes, mainframes, or early Unix hacking, —a raw, text-based window into another machine.
But as a learning tool ? Absolutely. Telnet is the "Hello World" of network protocols. And writing it in Lisp is like learning to cook by making bread from scratch—you understand every ingredient.