Ports
Intro to Ports
In computer networking, a port is a virtual communication endpoint — like a numbered “door” that allows specific types of network traffic to enter or leave a device.
1. What a Port Is
Every device on a network has an IP address (like a street address).
Each application or service running on that device “listens” on a port number (like a specific apartment number).
Ports help your computer know which program should handle incoming or outgoing data.
For example:
The IP address identifies the device.
The port number identifies the service or process on that device.
So, when you connect to a website, your computer sends data to:
IP address:port numberlike 142.250.191.46:443 (Google’s IP on HTTPS port).
2. What Ports Do
Ports organize and manage multiple network connections happening at the same time. They allow different applications to use the network without interfering with each other.
For example:
Web browser uses port 80 (HTTP) or 443 (HTTPS)
Email client uses port 25 (SMTP) or 993 (IMAP)
File Transfer Protocol uses port 21 (FTP)
Your computer can be downloading a file, streaming music, and browsing the web simultaneously — each using different ports.
3. Types of Ports
There are 65,535 total ports for each IP address:
Well-known ports (0–1023): Reserved for common services e.g., HTTP (80), HTTPS (443), FTP (21), DNS (53)
Registered ports (1024–49151): Used by user or vendor-specific apps e.g., MySQL (3306), RDP (3389)
Dynamic/private ports (49152–65535): Used temporarily by applications when making outbound connections
4. Example
If you type https://example.com in a browser:
DNS resolves “example.com” to an IP address.
Your browser connects to that IP address on port 443 (HTTPS).
The web server listens on port 443, accepts the request, and sends back the webpage.
Common Ports
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