Hypertext Transfer Protocol - unencrypted web traffic

HTTP Secure - encrypted web traffic using TLS/SSL

Common alternative HTTP port, often used for proxies and dev servers

Common alternative HTTPS port

Simple Mail Transfer Protocol - email sending between servers

SMTP over implicit TLS/SSL - secure email submission

Email submission with STARTTLS - recommended for sending email

Post Office Protocol v3 - email retrieval (downloads and deletes)

POP3 over TLS/SSL - secure email retrieval

Internet Message Access Protocol - email access (keeps on server)

IMAP over TLS/SSL - secure email access

FTP data transfer channel (active mode)

FTP command/control channel

Secure Shell and SSH File Transfer Protocol

Trivial File Transfer Protocol - simple, no authentication

FTP data over TLS/SSL

FTP control over TLS/SSL

Domain Name System - resolves domain names to IP addresses

Encrypted DNS queries over TLS (DoT)

Unencrypted remote terminal access (insecure, use SSH instead)

Remote Desktop Protocol - Windows remote desktop

Virtual Network Computing - remote desktop sharing

MySQL / MariaDB database server

PostgreSQL database server

Microsoft SQL Server

Oracle Database default listener

MongoDB NoSQL database server

Redis in-memory data store

Elasticsearch REST API

Apache CouchDB REST API

Advanced Message Queuing Protocol (RabbitMQ)

Apache Kafka message broker

Message Queuing Telemetry Transport - IoT messaging

MQTT over TLS/SSL

Dynamic Host Configuration Protocol - server to client

Dynamic Host Configuration Protocol - client to server

Network Time Protocol - clock synchronization

Simple Network Management Protocol - device monitoring

SNMP notifications from devices to management station

System logging protocol

Lightweight Directory Access Protocol

LDAP over TLS/SSL

Internet Key Exchange - IPsec VPN negotiation

IPsec NAT Traversal

OpenVPN default port

WireGuard VPN default port

Common development server port (Node.js, React, etc.)

Angular CLI default development server

Vite development server default port

Common Python/Django development server

Prometheus monitoring server

Grafana Loki log aggregation

Docker daemon API (unencrypted)

Docker daemon API (encrypted)

Kubernetes API server

Kubernetes Kubelet API

etcd client communication

Kerberos authentication system

Server Message Block - Windows file sharing

Apple Filing Protocol - macOS file sharing

rsync file synchronization

SOCKS proxy protocol

Squid HTTP proxy default port