It's a fact of life that MT4 occasionally gets disconnected from the broker's server. These problems usually resolve themselves quickly, but MT4 sometimes needs to be restarted in order to re-establish a connection.

The MT4 Auto-restart EA watches for these connection issues. It can be configured to send alerts, and also to restart MT4 automatically if there is a problem. This restart is usually enough to resolve the problem and re-establish the connection.

N.B. If your server completely loses its connection to the internet, then restarts clearly will not help, and alerts cannot be delivered. The Account Monitor can be used to provide an extra level of protection: remote monitoring of the health and availability of your MT4 installation, notifying you if your server goes down.