What is a Port? – Network Ports Explained

What is a network port?

A network port is a virtual endpoint for network communication. While an IP address identifies a device on the network, a port number identifies a specific service or application running on that device. Think of it like an apartment building: the IP address is the building address, and the port is the apartment number.

Port numbers range from 0 to 65535 and are used by both TCP and UDP protocols.

Range0 – 65535

Well-known ports0 – 1023

Registered ports1024 – 49151

Dynamic ports49152 – 65535

Well-known ports

Port	Protocol	Service	Description
21	TCP	FTP	File Transfer Protocol
22	TCP	SSH	Secure Shell – encrypted remote access
25	TCP	SMTP	Sending emails
53	UDP/TCP	DNS	Domain Name System
80	TCP	HTTP	Unencrypted web traffic
443	TCP	HTTPS	Encrypted web traffic (SSL/TLS)
587	TCP	SMTP/TLS	Sending emails (encrypted)
3306	TCP	MySQL	MySQL database
3389	TCP	RDP	Windows Remote Desktop
5432	TCP	PostgreSQL	PostgreSQL database

Open vs closed ports

Open port A service is listening and accepting connections

Closed port No service listening – connection refused

Filtered port Firewall blocking – no response at all

Databases (MySQL, PostgreSQL, MongoDB) and remote access services (RDP, SSH) should never be publicly accessible unless absolutely necessary. Use our Port Check tool to verify your server's exposure.

Related tools

Port Check Ping Test TCP vs UDP

Knowledge Port Check Ping Test DNS Lookup My IP

Network ports – directing traffic to the right service

Every network service runs on a specific port number. The combination of IP address and port (e.g. 192.168.1.1:80) uniquely identifies a network endpoint. Well-known ports (0-1023) are reserved for standard services like HTTP (80), HTTPS (443) and SSH (22). Open ports that are not needed should be closed with a firewall to reduce the attack surface of your server.