Connection monitor enables you to monitor communication between two separate VMs so that you're notified when there are any issues in the network connection between them. To use this feature, go to the Connection monitor blade and click on the + Add button to install the monitor:
Figure 6.14 – Adding a connection monitor
Besides the aforementioned fields, you can use advanced settings such as a source port and probing interval. This will allow you to leverage custom configuration (if you have very specific requirements when it comes to open ports). Check out the following link for a more detailed approach: https://docs.microsoft.com/en-us/azure/network-watcher/connection-monitor-preview.
Note that this service works not only for Azure VMs but also for applications (by using Application Insights). Proper monitoring configuration is crucial for all the systems as it allows you to quickly react to issues and investigate...