TinyWall - Lightweight and non-intrusive firewall
Zabbix - Track, record, alert and visualize performance and availability of IT resources
Windows 10 Firewall Control - Windows 10 Firewall Control: simple and exhaustive solution for applications network activity controlling and monitoring.
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
Emsisoft Online Armor Firewall - Emsisoft Online Armor Firewall is a freemium online firewall protection system by the Emsisoft that is based on the own independent protection technology of the Emsisoft.
Prometheus - An open-source systems monitoring and alerting toolkit.