Warn user about multiple instance of STK server

src/network/network.cpp

@@ -55,7 +55,8 @@ Network::Network(int peer_count, int channel_limit,
     if (!m_host)
     {
         Log::fatal("Network", "An error occurred while trying to create an "
-                   "ENet client host.");
+                   "ENet client host, maybe you started multiple instance "
+                   "of STK server?");
     }
 }   // Network
 
@@ -215,4 +216,4 @@ void Network::closeLog()
         m_log_file.getData() = NULL;
         m_log_file.unlock();
     }
-}   // closeLog
+}   // closeLog