Data commit

Task/Echo-server/Scheme/echo-server.ss

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+; Needed in Guile for read-line
+(use-modules (ice-9 rdelim))
+
+; Variable used to hold child PID returned from forking
+(define child #f)
+
+; Start listening on port 12321 for connections from any address
+(let ((s (socket PF_INET SOCK_STREAM 0)))
+  (setsockopt s SOL_SOCKET SO_REUSEADDR 1)
+  (bind s AF_INET INADDR_ANY 12321)
+  (listen s 5) ; Queue size of 5
+
+  (simple-format #t "Listening for clients in pid: ~S" (getpid))
+  (newline)
+
+; Wait for connections forever
+  (while #t
+    (let* ((client-connection (accept s))
+        (client-details (cdr client-connection))
+        (client (car client-connection)))
+; Once something connects fork
+      (set! child (primitive-fork))
+      (if (zero? child)
+      (begin
+; Then have child fork to avoid zombie children (grandchildren aren't our responsibility)
+        (set! child (primitive-fork))
+        (if (zero? child)
+          (begin
+; Display some connection details
+          (simple-format #t "Got new client connection: ~S" client-details)
+          (newline)
+          (simple-format #t "Client address: ~S"
+            (gethostbyaddr (sockaddr:addr client-details)))
+          (newline)
+; Wait for input from client and then echo the input back forever (or until client quits)
+          (do ((line (read-line client)(read-line client))) ((zero? 1))
+            (display line client)(newline client))))
+; Child exits after spawning grandchild.
+        (primitive-exit))
+; Parent waits for child to finish spawning grandchild
+      (waitpid child)))))