Set 1 — Ports and Protocols

FTP

Ports 20 (data) & 21 (control) - file transfer, unencrypted

SSH

Port 22 - secure encrypted remote login/terminal

Telnet

Port 23 - remote login, plain text (insecure, old SSH)

SMTP

Port 25 - sending outgoing email

DNS

Port 53 - translates domain names to IP addresses

DHCP

Ports 67 (server) & 68 (client) - auto-assigns IP addresses

TFTP

Port 69 - simple/trivial file transfer, no login, used for firmware

HTTP

Port 80 - unencrypted web traffic

POP3

Port 110 - downloads email from server (usually deletes it after)

NTP

Port 123 - synchronizes time between devices

NetBIOS/NetBT

Ports 137 & 139 - Windows file/printer sharing (legacy)

IMAP

Port 143 - manages/reads email directly on the server

SNMP

Ports 161 (query) & 162 (trap/alert) - monitors network devices

LDAP

Port 389 - directory services (e.g. Active Directory lookups)

HTTPS

Port 443 - encrypted web traffic (HTTP + TLS/SSL)

SMB/CIFS

Port 445 - Windows file & printer sharing

Syslog

Port 514 - centralized log collection

LDAPS

Port 636 - secure/encrypted LDAP

SMTPS

Port 465 or 587 - secure/encrypted SMTP

IMAPS

Port 993 - secure/encrypted IMAP

POP3S

Port 995 - secure/encrypted POP3

SQL Server

Port 1433 - Microsoft SQL database traffic

RDP

Port 3389 - remote GUI control of a Windows computer

TCP

Connection-oriented, 3-way handshake, confirms delivery = reliable but slower

UDP

Connectionless, no handshake/confirmation = fast but unreliable

Well-known ports

0-1023 (reserved for common protocols like HTTP, FTP, DNS)

Registered ports

1024-49151 (assigned to specific applications/vendors)

Dynamic/private ports

49152-65535 (temporary, used by client-side connections)

Datagram

A packet of data sent without waiting for an acknowledgment (used by UDP)