New TCP example

os2-tcp-test-date-service.rkt

@@ -0,0 +1,40 @@
+#lang racket/base
+;; Differently 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
+    (role 'date-sender (topic-publisher (tcp-channel local-addr remote-addr (wild)))
+      #:state state)
+    (send-message (tcp-channel local-addr remote-addr
+			       (string->bytes/utf-8
+				(format "~a\n" (current-inexact-milliseconds)))))
+    (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)