Network Ports

  1. Windows Tools

Ports can be generalized into one of three states:
  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.

General Introduction

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.

How can you find out which process is listening on a port on Windows?

How to verify that a UDP port is open?

Internet Control Message Protocol (ICMP) Parameters

Windows Tools

Download TCPView here:

Download nmap here:


Glenn Lyons VK4PK
Ver:gnl20190228 - pre published v0.9