Network Ports

1. Windows Tools

1. Open or Accepted: The host sent a reply indicating that a service is listening on the port.
2. Closed or Denied or Not Listening: The host sent a reply indicating that connections will be denied to the port.
3. Filtered, Dropped or Blocked: There is no reply from the host.

In security parlance, the term open port is used to mean a TCP or UDP port number that is configured to accept packets. In contrast, a port which rejects connections or ignores all packets directed at it is called a closed port.
Source: https://en.wikipedia.org/wiki/Open_port

How can you find out which process is listening on a port on Windows?
https://stackoverflow.com/questions/48198/how-can-you-find-out-which-process-is-listening-on-a-port-on-windows

How to verify that a UDP port is open?
https://networkengineering.stackexchange.com/questions/26541/how-to-verify-that-a-udp-port-is-open

Internet Control Message Protocol (ICMP) Parameters
http://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml

Windows Tools