Network port Fundamentals

Ip addresses street address.

ports bedroo, kitchen ect.

Port: Logical opening in a computer that represents a service or applicaion.

Ports in a computer network: nUmbered from 0, to 65,535

Well known ports 0 - 1,023.. 80,443, 53 ect.

Registered ports -registired with IANA

Ephemeral ports. - short lived temp ports which are opened just for a small period of tiem for an application from 49,152

so a client will always send to the well known port but will use an ephermerial port to send it from.

🎯 Ports & Port Ranges – Key to Network Services

Analogy:

IP Address = Street Address (where the device lives)
Port = Room Number (which service/app you're trying to reach)

🧩 What is a Port?

A logical number that identifies a specific service or application running on a system.

Helps direct traffic to the correct process.

🔢 Port Range Breakdown

| Type | Range | Description | | --- | --- | --- | | Well-known Ports | 0–1023 | Assigned to common protocols (HTTP, HTTPS, DNS, etc.) | | Registered Ports | 1024–49151 | Used by vendors/app developers (e.g., MS SQL, Oracle) | | Ephemeral Ports | 49152–65535 | Temporary, client-side ports used when initiating a connection |

🧠 Clients send from an ephemeral port → to a well-known or registered port on the server

📡 Real-World Example

Visiting a Website:

Client uses ephemeral port (e.g., 49500)
Sends request to port 443 (HTTPS) on the web server
Server replies to client’s ephemeral port

🧠 Memory Trick

Ephemeral = Expires Quickly (short-lived)

Well-known = Widely Used (HTTP, DNS, etc.)

💡 Common Well-Known Ports

| Port | Protocol | Description | | --- | --- | --- | | 20/21 | FTP | File Transfer Protocol | | 22 | SSH | Secure Shell | | 23 | Telnet | Unencrypted remote login | | 25 | SMTP | Sending email | | 53 | DNS | Domain Name System | | 67/68 | DHCP | Dynamic Host Configuration | | 80 | HTTP | Web (unencrypted) | | 110 | POP3 | Email retrieval | | 123 | NTP | Time sync | | 143 | IMAP | Email retrieval | | 443 | HTTPS | Web (secure) | | 3389 | RDP | Remote Desktop |

⚡ Rapid Review Questions

What range are ephemeral ports in?

→ 49152–65535
Do clients send to or from ephemeral ports?

→ From ephemeral ports (to well-known/registered ports)
What type of port is port 443?

→ Well-known port (HTTPS)
What is the purpose of a port?

→ Directs traffic to the correct application/service