Port Number Lookup: Which Service Runs Where
Every network service is reachable through a specific port number — some assigned by official IANA registration, others just widely-adopted convention among developers and tools. This searchable reference covers the ports you'll actually run into day to day: standard internet protocols, common databases, and popular local dev server defaults.
Ports 0-1023 are IANA well-known ports; higher ranges are registered or dynamic/private.
Well-Known vs. Convention-Based Ports
Ports below 1024 are formally registered with IANA for specific protocols — 443 for HTTPS isn't a convention, it's the standard. Ports above that (like 3000 for a React dev server, or 8080 as a generic 'alternate HTTP') are just widely-adopted community conventions, not official assignments, which is why you'll see some overlap and inconsistency between different tools' defaults.
Why Some Services Have Both a Plain and TLS Port
Many protocols have a legacy plaintext port and a separate, newer port for the TLS-encrypted version — HTTP (80) and HTTPS (443), SMTP (25) and SMTPS (465), IMAP (143) and IMAPS (993), FTP (21) and FTPS (990). This split exists so that both versions can run simultaneously on the same host without conflicting.
TCP vs. UDP: Different Port Spaces
It's a common misconception that a port number is globally unique — TCP and UDP actually maintain entirely separate port spaces, so a service can bind to TCP port 53 and a completely different service can independently bind to UDP port 53 on the same machine without conflict. DNS itself uses both, for different query types.
Practical Examples
Identifying an Unfamiliar Port in a Log
Quick lookup while debugging.
- 1.See traffic on port 6379 in a firewall log
- 2.Look it up: Redis in-memory data store
- 3.Confirm whether that traffic is expected
Choosing a Dev Server Port
Avoiding a conflict with another local service.
- 1.Default 3000 already in use
- 2.Check common alternates: 4000, 5000, 8000
- 3.Pick one unlikely to conflict with other local tools
Categories Covered
- Core internet protocols: HTTP, HTTPS, SSH, DNS, SMTP
- Databases: MySQL, PostgreSQL, MongoDB, Redis
- Dev tools: common Node/React/Flask dev server ports
- Infrastructure: Kafka, Elasticsearch, Kubernetes API
Good Use Cases
- Identifying an unfamiliar port in a firewall or traffic log
- Picking a dev server port unlikely to conflict locally
- Quickly recalling which port a specific database uses
- Learning the difference between a service's plain and TLS port
Frequently Asked Questions
What are 'well-known ports'?
Ports 0-1023 are officially registered with IANA for specific standard services (like 22 for SSH, 80 for HTTP, 443 for HTTPS) — operating systems typically require elevated privileges to bind to them, which is part of why they're trusted as identifying a specific service.
Why do development servers use such varied ports (3000, 5000, 8080)?
These are conventions established by specific frameworks and tools rather than any official standard — React's create-react-app popularized 3000, Flask defaults to 5000, and 8080 has long been a common 'alternate HTTP' choice specifically because ports below 1024 need elevated privileges on most systems.
What's the difference between TCP and UDP for a given service?
TCP is connection-oriented and guarantees delivery order (used for things like HTTP, SSH, and databases where reliability matters). UDP is connectionless and doesn't guarantee delivery or order, favored for latency-sensitive or broadcast-style traffic like DNS queries and NTP time sync.
Can two services actually use the same port number?
Not simultaneously on the same host and protocol — but the same port number can be used by different services on TCP vs UDP (they're actually separate port spaces), or reused freely across different machines, which is why port numbers alone don't uniquely identify a service without also knowing the host and protocol.
Why is port 22 also listed with an alternate at 2222?
2222 is a common convention for a secondary/non-default SSH port, often used to reduce automated brute-force scanning traffic that targets the well-known port 22, or when the default port is already in use by another service on the same host.
Is this list exhaustive?
No — it covers the ports developers most commonly encounter (standard internet services, common databases, popular dev tools). The full IANA registry has thousands of registered ports for much more specialized protocols.