🔌 TCP / UDP Port Database Reference
Search common TCP/UDP network ports (22, 80, 443, 3306, 5432, 8080) with protocol definitions, standard service names, and security recommendations.
69 of 69 ports
Port ranges are set by IANA: 0–1023 well-known, 1024–49151 registered, 49152–65535 dynamic. A registered assignment is a convention, not an enforcement — anything can listen on any free port, which is why a port number tells you what a service probably is rather than what it definitely is. The risk labels here are about exposure to the open internet; on a private network with proper segmentation the calculus is different.
What TCP / UDP Port Database Reference Does
A port number is a sixteen-bit label that lets one machine run many network services at once. There are 65,536 of them, and IANA divides the range into three parts: 0 to 1023 well-known, 1024 to 49151 registered, and 49152 to 65535 dynamic.
The distinction that actually matters day to day is the first boundary. On Unix-like systems, binding a port below 1024 requires root, which is why web servers historically started as root and dropped privileges, and why development servers default to 3000 or 8080 instead of 80.
An IANA assignment is a convention, not an enforcement. Anything can listen on any free port, and plenty of software ignores its registration. So a port number tells you what a service probably is, never what it definitely is — which is why a port scan is a starting point for investigation rather than an answer.
The question most people are actually asking is not "what is port 3389" but "should this be open". That is a different question with a fairly consistent answer: database ports, remote-desktop ports and management interfaces should not face the public internet, and most of the well-known breaches of the last decade involved one that did.
How to Use TCP / UDP Port Database Reference
- Click a quick port shortcut or type a port number/service in the search bar
- Review service descriptions, protocol types, and security recommendations
Formula Used by TCP / UDP Port Database Reference
The three ranges
0–1023 well-known · 1024–49151 registered · 49152–65535 dynamic and ephemeral
- well-known
- assigned by IANA; binding one needs root on Unix-like systems
- registered
- registered for a service but bindable by any user
- dynamic
- never assigned; the operating system picks from here for the client end of outbound connections
Worked example
A browser connecting to a website.
- The server listens on 443, a well-known port
- The operating system assigns the browser a source port from the dynamic range
- The connection is identified by the pair of addresses and the pair of ports
Result: That is why one machine can hold hundreds of connections to the same server — each uses a different ephemeral source port.
The ports most often found exposed by mistake
Each of these has a documented history of mass compromise when reachable from the internet.
| Port | Service | Why it matters |
|---|---|---|
| 445 | SMB | The path WannaCry and NotPetya spread over |
| 3389 | RDP | Among the most brute-forced ports on the internet; a standard ransomware entry point |
| 27017 | MongoDB | Older versions bound to all interfaces with no authentication; tens of thousands were ransomed |
| 6379 | Redis | Historically no authentication by default; exposed instances get cryptomined within hours |
| 9200 | Elasticsearch | Unsecured clusters have leaked billions of records |
| 11211 | Memcached | UDP memcached produced record-breaking amplification attacks in 2018 |
| 2375 | Docker API | Unauthenticated access is equivalent to root on the host |
| 5900 | VNC | Frequently deployed with no password at all |
| 23 | Telnet | Entirely unencrypted; the basis of the Mirai botnet |
Encrypted and unencrypted pairs
Where a protocol has both, the unencrypted one should generally be closed.
| Unencrypted | Encrypted | Protocol |
|---|---|---|
| 21 FTP | 22 SFTP | File transfer |
| 23 Telnet | 22 SSH | Remote shell |
| 80 HTTP | 443 HTTPS | Web |
| 110 POP3 | 995 POP3S | Mail retrieval |
| 143 IMAP | 993 IMAPS | Mail access |
| 389 LDAP | 636 LDAPS | Directory |
| 1883 MQTT | 8883 MQTTS | IoT messaging |
How to Read Your Result
Bind to localhost rather than firewalling
For a database or cache that only local processes need, binding to 127.0.0.1 is stronger than a firewall rule, because it cannot be undone by a misconfigured rule later. Redis, MongoDB and Postgres all default this way now, precisely because of what happened when they did not.
A closed port and a filtered port are different
Closed means the machine actively refused; filtered means something dropped the packet silently. Scanners distinguish them, and the difference tells you whether a firewall exists between you and the host — which is often more informative than the port list itself.
Changing the port is not security
Moving SSH to 2222 reduces log noise from automated scans, and that is all it does. Everything is scanned across the full range; obscurity buys nothing against a targeted attempt. Key-based authentication does the actual work.
Ephemeral ports are a finite resource
A machine making very many outbound connections can exhaust its ephemeral range, which surfaces as connection failures under load with no obvious cause. It is a common and confusing failure mode in load generators and busy proxies.
Limitations & Accuracy Notes
- A curated reference of common ports, not the complete IANA registry, which lists thousands of assignments.
- Assignments are conventions; software can and does listen on unregistered ports.
- Risk labels describe exposure to the open internet. On a segmented private network the assessment differs.
- Some numbers carry several services; the entries here list the common ones rather than every claimant.
- Nothing here scans anything. It is a lookup, not a diagnostic of your machine.
Frequently Asked Questions
What are port numbers used for in networking?
What are the well-known ports?
What are the port number ranges?
Why do well-known ports need elevated privileges?
Does a port number guarantee which service is running?
What is the difference between TCP and UDP on the same port?
Should I change SSH off port 22?
Is this a port scanner?
References & Further Reading
- IANA — Service Name and Transport Protocol Port Number Registry — The authoritative registry and the definition of the three ranges
- RFC 6335 — port number procedures — Formalizes the well-known, registered and dynamic ranges