diff -urN knockd-0.5/src/knockd.c knockd-0.5.new/src/knockd.c
--- knockd-0.5/src/knockd.c	2005-06-27 07:11:34.000000000 +0200
+++ knockd-0.5.new/src/knockd.c	2009-03-10 00:24:25.000000000 +0100
@@ -26,6 +26,7 @@
 #include <signal.h>
 #include <time.h>
 #include <ctype.h>
+#include <limits.h>
 #include <string.h>
 #include <fcntl.h>
 #include <netinet/in.h>