Ports and Protocols 2.1

Port

A numbered “door” on a device that tells the host where to send or receive specific types of traffic.

FTP (File Transfer Protocol)

Used to transfer files between a client and server; uses port 21 for control and port 20 for data.

SSH (Secure Shell)

Runs on port 22; allows secure remote login and encrypted communication between devices.

Telnet

Uses port 23; allows remote login to a device but does not encrypt communication.

RDP (Remote Desktop Protocol)

Runs on port 3389; lets you see a remote computer's display and use your keyboard/mouse to control it.

NetBIOS (Network Basic Input/Output System)

Used for local file sharing and communication; port 137 for info transfer, port 139 for establishing connections; requires unique computer names.

SMB (Server Message Block)

Uses port 445; allows file sharing and data transfer, commonly implemented in Windows networks via CIFS.

SMTP (Simple Mail Transfer Protocol)

Uses port 25; used to send email.

IMAP (Internet Message Access Protocol)

port 143; lets you access emails while keeping them on the server.

POP3 (Post Office Protocol version 3)

Uses port 110; downloads emails to local computer and removes them from the server.

DNS (Domain Name System)

Uses port 53; translates hostnames into IP addresses and vice versa.

LDAP (Lightweight Directory Access Protocol)

Uses port 389; accesses directory services like usernames, passwords, and computer accounts.

HTTP (HyperText Transfer Protocol)

Uses port 80; transfers web pages without encryption.

HTTPS (HyperText Transfer Protocol Secure)

Uses port 443; transfers web pages with TLS encryption for security.

SNMP (Simple Network Management Protocol)

Uses ports 161 (manager to agent) and 162 (agent to manager); used to monitor and manage network devices.

TLS (Transport Layer Security)

A protocol that encrypts data sent over a network, verifies the server’s identity, and ensures data integrity, making communication secure