🔌 15 Most Common Protocols & Ports Every DevOps Engineer Should Know
Because if your service isn’t listening on the right port, is it even alive?
One of the first things I had to figure out as I got deeper into DevOps was this:
What protocols run where, and why does every tool ask about ports?!
So I made a cheat sheet — not just to remember the ports, but to understand why these protocols matter in DevOps day-to-day work.
This blog is that cheat sheet, cleaned up and shared. If you're doing the #90DaysOfDevOps2025 like me — here's your Protocols & Ports breakdown 👇
📖 What Are Protocols & Ports?
Before diving in, let’s get the basics out of the way:
A protocol is a set of rules for communication between devices. Think of it like a language (e.g., HTTP for web, SSH for remote login).
A port is like a channel inside a machine. Each protocol usually uses a default port — so tools and services know where to listen or talk.
For example, if you're serving a website over HTTPS, the server listens on port 443, and clients automatically expect it there.
📋 Most Common Protocols & Ports in DevOps
Here’s the core list I use again and again in projects, cloud deployments, CI/CD tasks, and container setups:
| Protocol | Port | Use Case | DevOps Relevance |
| HTTP | 80 | Unsecured web traffic | Serving sites, APIs, probes |
| HTTPS | 443 | Secured web traffic (TLS/SSL) | Hosting secure apps, frontend-backend comm |
| SSH | 22 | Remote terminal login | Server access, Git over SSH |
| FTP | 21 | File transfer | Legacy systems, rare in modern pipelines |
| SFTP | 22 | Secure FTP (over SSH) | Transferring logs securely |
| DNS | 53 | Resolves domain names | Custom domains, service discovery |
| SMTP | 25 | Sending emails | Alerting, notification systems |
| POP3 | 110 | Receiving emails | Rare, legacy support |
| IMAP | 143 | Receiving emails (advanced) | Email alerts integration |
| MySQL | 3306 | MySQL DB access | Database connections in apps |
| PostgreSQL | 5432 | PostgreSQL DB access | Common in SaaS & cloud-native tools |
| MongoDB | 27017 | NoSQL DB access | Storing logs, events, analytics data |
| Redis | 6379 | In-memory data store | Caching, pub/sub, job queues |
| Elasticsearch | 9200 | Search engine queries | Log storage (e.g., ELK stack) |
| Kubernetes API | 6443 | Cluster management | Used by kubectl, CI tools, etc. |
🔍 Why These Matter in DevOps Workflows
Let’s break down where you’ll actually touch these protocols:
1. 🔐 SSH (Port 22)
Used constantly for accessing remote servers or containers.
Set up automation scripts to SSH into EC2 or VPS
Connect GitHub/GitLab via SSH keys
Diagnose services directly from terminal
2. 🌐 HTTP / HTTPS (Ports 80/443)
Runs everything on the web — your backend, frontend, dashboards, APIs.
Expose services in Docker/Kubernetes with ingress
Set up reverse proxies using NGINX
Monitor apps using HTTP health checks
3. 🛢️ Databases (3306, 5432, 27017)
Your apps need data — securely and consistently.
Connect CI/CD pipelines to test DBs
Use managed DBs in AWS, GCP, Azure
Configure
.envfiles with DB ports in containers
4. 🧠 Caching & Search (6379, 9200)
Used for performance tuning and log storage.
Redis queues for background jobs
Elasticsearch for central log monitoring (e.g., ELK/EFK stacks)
Observability tools like Grafana rely on these
5. 📩 Email Protocols (25, 110, 143)
Used when your app or server needs to send or receive alerts.
SMTP for sending alert emails
Integrating tools like Postfix or Mailgun
Emailing build logs or failure reports
6. 🧭 DNS (Port 53)
A misconfigured DNS record can break everything.
Setup DNS in Route 53 or Cloudflare
Use
digornslookupduring troubleshootingLink custom domains to cloud services
🧪 Bonus: DevOps Port Troubleshooting Tip
When something isn’t working, I always do this first:
bashCopyEdit# Check if port is open
nc -zv <hostname> 22
# Or test HTTP/HTTPS endpoint
curl -I http://your-api.com
# For DNS
dig yourdomain.com
Sometimes it’s just a closed port in your firewall or security group.