🛡️ Core Connectivity & Shells
20
FTP Data
Actual file transfer channel
TCP
21
FTP Control
Commands / Authentication (Insecure)
TCP
22
SSH
Secure Shell — remote login, SFTP, SCP
TCP
23
Telnet
Insecure remote terminal access
TCP
🌐 Web & Directory Services
53
DNS
Domain Name System — name resolution
UDP (queries), TCP (zone transfers)
80
HTTP
Unencrypted web traffic
TCP
88
Kerberos
AD authentication / ticketing
TCP, UDP
389
LDAP
Directory service queries
TCP, UDP
443
HTTPS
Secure web traffic (TLS)
TCP
🪟 Windows & Infrastructure
135
Microsoft EPMAP
RPC Endpoint Mapper
TCP, UDP
136–139
NetBIOS
Legacy Windows file & name services
TCP, UDP
445
SMB / Microsoft-DS
Modern file sharing and Active Directory services
TCP
515
LPD
Line Printer Daemon
TCP
📧 Email & Time
25
SMTP
Email delivery & routing
TCP
110
POP3
Retrieval from mail server (older)
TCP
143
IMAP
Message access & syncing
TCP
123
NTP
Network Time Protocol
UDP
📊 Databases & Auth
1433
MS SQL Server
SQL Server database engine
TCP
1434
MS SQL Monitor
SQL Browser / monitoring service
UDP (listener), TCP
1521
Oracle Listener
Oracle database connection listener
TCP
1812 / 1813
RADIUS
Authentication (1812) & Accounting (1813)
UDP
🛠️ Management & IP
67 / 68
DHCP
Server / Client — automatic IP assignment
UDP
69
TFTP
Trivial FTP — simple file transfers (boot/config)
UDP
161 / 162
SNMP / Traps
Network management (queries and traps)
UDP (161 queries), UDP (162 traps)
500
ISAKMP / IKE
VPN tunnel negotiation (IKEv1/IKEv2)
UDP (commonly)