Use actor macro

minimart/examples/udp-hello.rkt

@@ -4,13 +4,8 @@
 
 (spawn-udp-driver)
 
-(spawn (lambda (e s)
-	 (match e
-	   [(message (udp-packet src dst body) _ _)
-	    (log-info "Got packet from ~v: ~v" src body)
-	    (transition s (send (udp-packet dst
-					    src
-					    (string->bytes/utf-8 (format "You said: ~a" body)))))]
-	   [_ #f]))
-       (void)
-       (gestalt-union (sub (udp-packet ? (udp-listener 5999) ?))))
+(actor #:name echoer
+       (subscribe (udp-packet ($ src) ($ dst (udp-listener 5999)) ($ body))
+	 (log-info "Got packet from ~v: ~v" src body)
+	 (define reply (string->bytes/utf-8 (format "You said: ~a" body)))
+	 (send (udp-packet dst src reply))))