Define timeout as a const.

coupler/opc-ua-server/keep_alive.h

@@ -5,6 +5,9 @@ static unsigned int HEART_BEATS = 0;
 const int DEFAULT_HEART_BEAT_INTERVAL = 250;
 static int HEART_BEAT_INTERVAL = DEFAULT_HEART_BEAT_INTERVAL;
 
+// the timeout in millis after which a coupler is considered down
+const int DEFAULT_HEART_BEAT_TIMEOUT_INTERVAL = 4 * DEFAULT_HEART_BEAT_INTERVAL;
+
 // the list of couplers onto which we depend for properly running$
 // XXX: assume ONLY 8 couplers!
 unsigned int HEART_BEAT_ID_LIST[] = {0, 0, 0, 0, 0, 0, 0, 0};

coupler/opc-ua-server/keep_alive_subscriber.h

@@ -276,7 +276,7 @@ void callbackCheckHeartBeat() {
         // we do have timestamp for this coupler ID
         int last_seen_timestamp_int = atoi(last_seen_timestamp);
         int timestamp_delta = milli_seconds - last_seen_timestamp_int;
-        bool is_down = (timestamp_delta > 1000);
+        bool is_down = (timestamp_delta > DEFAULT_HEART_BEAT_TIMEOUT_INTERVAL);
         if (is_down) {
           UA_LOG_INFO(UA_Log_Stdout, \
                       UA_LOGCATEGORY_USERLAND, \