Skip to content

What is a port?

A port is a virtual point where network connections start and end. Ports are software-based and managed by a computer's operating system. Each port is associated with a specific process or service. Ports allow computers to easily differentiate between different kinds of traffic: emails go to a different port than webpages, for instance, even though both reach a computer over the same Internet connection.

Ports are standardized across all network-connected devices, with each port assigned a number. Most ports are reserved for certain protocols for example messages go to port 80. While IP_Address enable messages to go to and from specific devices, port numbers allow targeting of specific services or applications within those devices.

TCP Ports

  • 21: FTP (File Transfer Protocol) - allows file transfer between systems.
  • 22: SSH (Secure Shell) - a secure network protocol that allows users to connect to and administer systems remotely.
  • 23: Telnet - a protocol used for remote connection to network devices.
  • 80: HTTP (Hypertext Transfer Protocol) - the protocol used for transferring data on the World Wide Web.
  • 443: HTTPS (Hypertext Transfer Protocol Secure) - the secure version of HTTP, which uses SSL/TLS encryption to protect web communications.
  • 3389:RDP (Remote Desktop Protocol) https://book.hacktricks.xyz/network-services-pentesting/pentesting-rdp

UDP Ports

  • 53: DNS (Domain Name System) - a system that translates domain names into IP addresses.
  • 67/68: DHCP (Dynamic Host Configuration Protocol) - a protocol used to assign IP addresses and other configuration parameters to devices on a network.
  • 69: TFTP (Trivial File Transfer Protocol) - a simple protocol used to transfer files between devices on a network.
  • 123: NTP (Network Time Protocol) - a protocol used to synchronize the clocks of devices on a network.
  • 161: SNMP (Simple Network Management Protocol) - a protocol used to manage and monitor devices on a network.