Changed NPDU handler to check for BACnet version before attempting to decode. Thanks, Piotr!

bacnet-stack/demo/handler/h_npdu.c

@@ -47,6 +47,8 @@ void npdu_handler(
     BACNET_ADDRESS dest = { 0 };
     BACNET_NPDU_DATA npdu_data = { 0 };
 
+    /* only handle the version that we know how to handle */
+    if (pdu[0] == BACNET_PROTOCOL_VERSION) {
         apdu_offset = npdu_decode(&pdu[0], &dest, src, &npdu_data);
         if (npdu_data.network_layer_message) {
             /*FIXME: network layer message received!  Handle it! */
@@ -54,26 +56,24 @@ void npdu_handler(
             printf("NPDU: Network Layer Message discarded!\n");
 #endif
         } else if ((apdu_offset > 0) && (apdu_offset <= pdu_len)) {
-        if ((npdu_data.protocol_version == BACNET_PROTOCOL_VERSION) &&
+            if ((dest.net == 0) || (dest.net == BACNET_BROADCAST_NETWORK)) {
-            ((dest.net == 0) || (dest.net == BACNET_BROADCAST_NETWORK))) {
                 /* only handle the version that we know how to handle */
                 /* and we are not a router, so ignore messages with
                    routing information cause they are not for us */
                 apdu_handler(src, &pdu[apdu_offset],
                     (uint16_t) (pdu_len - apdu_offset));
             } else {
-            if (dest.net) {
 #if PRINT_ENABLED
                 printf("NPDU: DNET=%u.  Discarded!\n", (unsigned)dest.net);
 #endif
+            }
+        }
     } else {
 #if PRINT_ENABLED
         printf("NPDU: BACnet Protocol Version=%u.  Discarded!\n", 
-                    (unsigned)npdu_data.protocol_version);
+            (unsigned)pdu[0]);
 #endif
     }
-        }
-    }
 
     return;
 }