Understanding important ports and how they differ.

 

Understanding important ports and how they differ from something like an Amazon RDS database port is essential for networking, DevOps, and cloud-related roles.

 The Concept of Ports in Networking

Ports are communication endpoints used to distinguish different services on a host. Think of them like "doors" for data to enter/leave a system.

• They range from 0 to 65535
• Divided into:
• Well-known ports (0–1023) – Standard services (e.g., HTTP, SSH)
• Registered ports (1024–49151) – Services/apps by vendors
• Dynamic/private ports (49152–65535) – Temporary use by clients

 Commonly Important Ports to Know

Service	Port	Protocol	Purpose
SSH	22	TCP	Secure remote login
HTTP	80	TCP	Web traffic (insecure)
HTTPS	443	TCP	Secure web traffic
FTP	21	TCP	File transfer
SFTP	22	TCP	Secure file transfer via SSH
SMTP	25/587	TCP	Sending email
DNS	53	TCP/UDP	Domain name resolution
DHCP	67/68	UDP	IP address assignment
SNMP	161/162	UDP	Network monitoring
MySQL	3306	TCP	MySQL DB communication
PostgreSQL	5432	TCP	PostgreSQL DB communication
RDP	3389	TCP	Remote desktop (Windows)
LDAP	389/636	TCP/UDP	Directory services (Active Directory)
Redis	6379	TCP	Redis DB
MongoDB	27017	TCP	MongoDB

 Amazon RDS Database Port

When using Amazon RDS (Relational Database Service), the port number depends on the database engine twtech may choose:

Database Engine	Default Port
MySQL / MariaDB	3306
PostgreSQL	5432
Oracle	1521
SQL Server	1433
Amazon Aurora	Depends on MySQL or PostgreSQL (3306 or 5432)

Difference:

• These ports are specific to the RDS database engine.
• The same ports are used if you were running the DB outside AWS.

In RDS context, twtech makes sure:

• Security groups allow inbound access to these ports.
• There is No public exposure unless absolutely necessary (twtech uses bastion/SSM if possible).

 twtech Summary of Differences

Aspect	General Port	RDS Port
Purpose	Handles various services (SSH, HTTP, etc.)	Handles DB traffic
Examples	22 (SSH), 80 (HTTP)	3306 (MySQL), 5432 (PostgreSQL)
Context	OS/Network services	Database engine-specific
Management	Firewall rules, OS configs	AWS security group rules, RDS settings