Common Port Reference for Opus Host VPS Users

Every service on your VPS listens on a port. This page is a cheat sheet: what each common port is for, and whether you should open it in your firewall.

Ports you will likely open

Port	Protocol	Service	Notes
22	TCP	SSH	Remote command line. Always allow this before enabling UFW
80	TCP	HTTP	Web traffic. Needed for Certbot’s HTTP challenge
443	TCP	HTTPS	Encrypted web traffic
25565	TCP	Minecraft Java	See Game Server
51820	UDP	WireGuard	Default WireGuard port. See WireGuard VPN

Ports blocked by default

Outbound mail ports are blocked on every new Opus Host VPS to prevent spam. Request an unblock if you have a legitimate reason.

Port	Protocol	Service	Notes
25	TCP	SMTP	Server-to-server mail
465	TCP	SMTPS	Legacy TLS submission
587	TCP	SMTP submission	Mail clients to servers

See Unblock Mail Ports.

Ports you should keep closed to the public

These are useful inside your VPS but should never be reachable from the public internet without a very good reason. Bind these services to 127.0.0.1 and put a reverse proxy in front if needed.

Port	Service	Why keep it private
3306	MySQL / MariaDB	Databases are prime brute-force targets
5432	PostgreSQL	Same as above
6379	Redis	Historically shipped with no auth
27017	MongoDB	Historically shipped with no auth
3000, 5000, 8000, 8080	Dev servers	Almost never meant for the public

See Databases and Nginx Reverse Proxy.

Well-known services

Port	Service
21	FTP
53	DNS
110	POP3
143	IMAP
993	IMAPS
995	POP3S
3389	RDP

Check what’s listening

See every port your VPS is currently listening on and which process owns it:

sudo ss -tulpn

Open or close a port

# Allow a port
sudo ufw allow 80/tcp

# Remove the rule
sudo ufw delete allow 80/tcp

# List current firewall rules
sudo ufw status verbose

Full firewall setup in Firewall.

Every open port is one more thing to keep patched. If you are not sure whether you need a port open, leave it closed — you can always allow it later.

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Common Port Reference for Opus Host VPS Users

Ports you will likely open

Ports blocked by default

Ports you should keep closed to the public

Well-known services

Check what’s listening

Open or close a port

​Ports you will likely open

​Ports blocked by default

​Ports you should keep closed to the public

​Well-known services

​Check what’s listening

​Open or close a port

Ports you will likely open

Ports blocked by default

Ports you should keep closed to the public

Well-known services

Check what’s listening

Open or close a port