Echo server: Difference between revisions

=={{header|Common Lisp}}==

Sockets is not a standard part of Common Lisp but many implementations have support for this. The following example {{works with|CLISP}}

<lang lisp>(defvar *clients* '()

"This is a list of (socket :input status) which is used with

`socket:socket-status' to test for data ready on a socket.")

(defun echo-server (port)

"Listen on `port' for new client connections and for data arriving on

any existing client connections"

(let ((server (socket:socket-server port)))

(format t "Echo service listening on port ~a:~d~%"

(socket:socket-server-host server)

(socket:socket-server-port server))

(socket:socket-options server :so-keepalive)

(unwind-protect

(loop

(when (socket:socket-status server 0 1)

(echo-accept-client (socket:socket-accept server

:external-format :dos

:buffered t)))

(when *clients*

(socket:socket-status *clients* 0 1)

(mapcar #'(lambda (client)

(when (eq :input (cddr client))

(echo-service-client (car client)))

(when (eq :eof (cddr client))

(echo-close-client (car client)))) *clients*)))

(socket-server-close server))))

(defun echo-accept-client (socket)

"Accept a new client connection and add it to the watch list."

(multiple-value-bind

(host port) (socket:socket-stream-peer socket)

(format t "Connect from ~a:~d~%" host port))

(push (list socket :input nil) *clients*))

(defun echo-service-client (socket)

(let ((line (read-line socket nil nil)))

(princ line socket)

(finish-output socket)))

(defun echo-close-client (socket)

"Close a client connection and remove it from the watch list."

(multiple-value-bind

(host port) (socket:socket-stream-peer socket)

(format t "Closing connection from ~a:~d~%" host port))

(close socket)

(setq *clients* (remove socket *clients* :key #'car)))

(echo-server 12321)

</lang>