For the longest time people have been asking about networking in Construct Classic. All these aspiring developers of the next great MMO can rejoice now, as Scidave did release the first alpha version of his plugin fittingly named 'Network'.
Although this is still an early release, working online games are already very much possible with this. I tried one or two sessions with Scidave's test game 'Net Shooter' myself and was impressed. While there are still some quirks to be worked out, hosting a game and making connections is a breeze.
Since there isn't built-in lag compensation or prediction, the man himself only recommends this plugin to use for not too action-oriented games (turn-based or similar). That shouldn't stop creative minds to come up with their own methods to make up for these lacking features.
Go gather all information and grab the plugin from the official thread.