Another example program

os2-tcp-test-echo-service.rkt

@@ -0,0 +1,46 @@
+#lang racket/base
+;; A more different trivial example program demonstrating os2-tcp.rkt.
+
+(require racket/string)
+(require racket/set)
+(require racket/match)
+(require "os2.rkt")
+(require "os2-tcp.rkt")
+
+(define ((connection-handler local-addr remote-addr) self-pid)
+  (transition 'no-state
+    (send-tcp-mode remote-addr local-addr 'lines)
+    (send-tcp-credit remote-addr local-addr 1)
+    (role 'echoer (topic-subscriber (tcp-channel remote-addr local-addr (wild)))
+      #:state state
+      [(tcp-channel remote _ (? bytes? line))
+       (transition state
+	 (send-tcp-credit remote-addr local-addr 1)
+	 (send-message
+	  (tcp-channel local-addr remote-addr (bytes-append #"You said: " line #"\n"))))]
+      [(tcp-channel remote _ (? eof-object?))
+       (transition state
+	 (kill))])))
+
+(define (listener local-addr)
+  (transition 'no-state
+    (role 'inbound-handler (topic-subscriber (tcp-channel (wild) local-addr (wild)) #:virtual? #t)
+      #:state state
+      #:topic t
+      #:on-presence (match t
+		      [(topic 'publisher (tcp-channel remote-addr (== local-addr) _) #t)
+		       ;; Ignore virtual flows. They just mean there's
+		       ;; someone willing to supply connections to us
+		       ;; at some point in the future.
+		       state]
+		      [(topic 'publisher (tcp-channel remote-addr (== local-addr) _) #f)
+		       (transition state (spawn (connection-handler local-addr remote-addr)))]))))
+
+(define (main port)
+  (ground-vm
+   (transition 'none
+     (spawn tcp-spy)
+     (spawn tcp-driver)
+     (spawn (listener (tcp-listener port))))))
+
+(main 5999)