Time for an 2014 update…

Task/Chat-server/00DESCRIPTION

@@ -1 +1,3 @@
 Write a server for a minimal text based chat. People should be able to connect via ‘telnet’, sign on with a nickname, and type messages which will then be seen by all other connected users. Arrivals and departures of chat members should generate appropriate notification messages.
+
+Nov. 31st is an interesting deadline :-) --[[User:Walterpachl|Walterpachl]] ([[User talk:Walterpachl|talk]]) 10:46, 2 November 2013 (UTC)

Task/Chat-server/Racket/chat-server.rkt

@@ -1,21 +1,37 @@
 #lang racket
 
-(define outs (list (current-output-port)))
-(define ((tell-all who o) line)
-  (for ([c outs] #:unless (eq? o c)) (displayln (~a who ": " line) c)))
+(define *client-outputs* (list (current-output-port)))
+
+(define ((tell-all who current-out) line)
+  (for ([out *client-outputs*] #:unless (eq? current-out out))
+    (displayln (~a who ": " line) out)))
+
+(define (serve-client input output)
+  (define nick (begin
+                 (display "Nick: " output)
+                 (read-line input)))
+  (define tell (tell-all nick output))
 
-(define ((client i o))
-  (define nick (begin (display "Nick: " o) (read-line i)))
-  (define tell (tell-all nick o))
   (let loop ([line "(joined)"])
-    (if (eof-object? line)
-      (begin (tell "(left)") (set! outs (remq o outs)) (close-output-port o))
-      (begin (tell line) (loop (read-line i))))))
+    (cond [(eof-object? line)
+           (tell "(left)")
+           (set! *client-outputs* (remq output *client-outputs*))
+           (close-output-port output)]
+          [else
+           (tell line)
+           (loop (read-line input))])))
 
 (define (chat-server listener)
-  (define-values [i o] (tcp-accept listener))
-  (for ([p (list i o)]) (file-stream-buffer-mode p 'none))
-  (thread (client i o)) (set! outs (cons o outs)) (chat-server listener))
+  (define-values [client-input client-output] (tcp-accept listener))
+  (file-stream-buffer-mode client-input 'none)
+  (file-stream-buffer-mode client-output 'none)
+  (thread (λ ()
+            (serve-client client-input client-output)))
+  (set! *client-outputs* (cons client-output *client-outputs*))
+  (chat-server listener))
 
-(void (thread (λ() (chat-server (tcp-listen 12321)))))
-((client (current-input-port) (current-output-port)))
+(define (start-server)
+  (chat-server (tcp-listen 12321)))
+
+(void (thread start-server))
+(client (current-input-port) (current-output-port))