Wireshark - Wireshark is a network protocol analyzer for Unix and Windows. It lets you capture and interactively browse the traffic running on a computer network.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
Winsock Packet Editor - WPE Pro is a packet editor.
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.
Nipper - Nipper - Neat Internet Protocol Packet EditoR - is a graphical packet generation tool.
packeth - packeth is GUI and CLI packet generator tool for ethernet.