moved #include <signal.h> to from networkhandler.c to main.c was forgotton in the restructuring process. Thanks to emliber for reporting this issue

src/ports/platform-pc/main.c

@@ -6,6 +6,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
+#include <signal.h>
 
 #include "networkhandler.h"
 #include "opener_api.h"

src/ports/platform-pc/networkhandler.c

@@ -9,7 +9,6 @@
 #include <unistd.h>
 #include <errno.h>
 #include <sys/time.h>
-#include <signal.h>
 
 #include <opener_api.h>
 #include "networkhandler.h"