Index: applications/present3D/Cluster.cpp
--- applications/present3D/Cluster.cpp.orig
+++ applications/present3D/Cluster.cpp
@@ -35,7 +35,7 @@
 #if defined(__linux)
     #include <unistd.h>
     #include <linux/sockios.h>
-#elif defined(__FreeBSD__) || defined(__DragonFly__) || defined(__FreeBSD_kernel__)
+#elif defined(__FreeBSD__) || defined(__DragonFly__) || defined(__FreeBSD_kernel__) || defined(__OpenBSD__)
     #include <unistd.h>
     #include <sys/sockio.h>
 #elif defined(__sgi)
@@ -351,7 +351,8 @@ void Receiver::sync( void )
     }
 
 #if defined(__linux) || defined(__FreeBSD__) || defined( __APPLE__ ) || \
-    defined(__DragonFly__) || defined(__FreeBSD_kernel__) || defined(__GNU__)
+    defined(__DragonFly__) || defined(__FreeBSD_kernel__) || defined(__GNU__) \
+    || defined(__OpenBSD__)
     socklen_t
 #else
     int