Zabbix - Track, record, alert and visualize performance and availability of IT resources
TCPView - TCPView is a Windows program that will show you detailed listings of all TCP and UDP endpoints on...
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.
CurrPorts - CurrPorts displays the list of all currently opened TCP/IP and UDP ports on your local computer.
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
TCP Optimizer - SpeedGuide.net - The Broadband Guide. Cable modems, DSL, Wireless, Network security. Free speed tweaks and TCP/IP tools for optimizing system performance.