Common Network Ports Cheat Sheet by bytebar

20/21	TCP — FTP (data/­con­trol). "FTP is 21, data rides 20"
22	TCP — SSH / SCP / SFTP. Secure remote — the secure 2's
23	TCP — Telnet. Insecure — never use, know why
25	TCP — SMTP. Sending email
53	TCP/UDP — DNS. UDP for lookups, TCP for zone transfers
67/68	UDP — DHCP (serve­r/c­lient). "DHCP gives, 67/68 delive­rs"
69	UDP — TFTP. Trivial — no auth, PXE boot
80	TCP — HTTP. Unencr­ypted web
110	TCP — POP3. Downloads email (deletes from server)
123	UDP — NTP. Time sync
143	TCP — IMAP. Email stays on server
161/162	UDP — SNMP (manag­er/­trap). Monitoring
389	TCP/UDP — LDAP. Directory lookups
443	TCP — HTTPS. Encrypted web
445	TCP — SMB/CIFS. Windows file sharing — ransomware loves it
636	TCP — LDAPS. LDAP over TLS
993	TCP — IMAPS. IMAP over TLS
995	TCP — POP3S. POP3 over TLS
1433	TCP — Microsoft SQL. Database default
3306	TCP — MySQL/­Mar­iaDB. Database default
3389	TCP — RDP. Windows remote desktop
5432	TCP — Postgr­eSQL. Database default
5900	TCP — VNC. Remote screen sharing

Telnet (23)	SSH (22)
FTP (21)	SFTP/SCP (22) or FTPS
HTTP (80)	HTTPS (443)
SNMP v1/v2 (161)	SNMP v3 (auth + encryp­tion)
POP3 (110) / IMAP (143)	POP3S (995) / IMAPS (993)

Send (SMTP)	Plain: 25 (587 submis­sion) → Secure: 465 (SMTPS)
Receiv­e/read	Plain: 110 POP3 / 143 IMAP → Secure: 995 / 993