Port 227 sits in a peculiar state: officially reserved by the Internet Assigned Numbers Authority (IANA) as part of a block spanning ports 225-241. It's not assigned to any service. It's not available for you to use. It simply exists, held in reserve.
What "Reserved" Means
In the IANA port registry, "Reserved" is a distinct state from "Assigned" or "Unassigned." 1
When a port is marked as reserved, it means:
- Not available for regular assignment — You can't apply to use it for your service
- Assigned to IANA itself — Held for special purposes
- Deliberately set aside — May be used to extend port ranges or for future protocol needs
Reserved ports aren't forgotten ports. They're intentionally kept empty.
The 225-241 Block
Port 227 belongs to a block of 17 consecutive ports (225-241) that are all marked as reserved in both TCP and UDP protocols. 2
The IANA registry jumps from port 224 (masqdialer) directly to "225-241 Reserved," then picks up again at port 242 (direct). This isn't an accident or oversight—it's a deliberate choice to hold this entire range in reserve.
Why this specific block? The registry doesn't say. But the fact that IANA reserved 17 consecutive ports in the precious well-known range suggests these might be held for future protocol extensions or special purposes that haven't materialized yet.
Well-Known Ports
Port 227 falls within the well-known ports range (0-1023), also called system ports. This is the most restricted range of the port space, where assignments require IETF Review or IESG Approval. 3
The well-known range includes:
- Port 22 — SSH
- Port 80 — HTTP
- Port 443 — HTTPS
- Port 227 — Reserved (held, not used)
Reserving space in this range isn't done lightly. Every port between 0 and 1023 is valuable real estate in the Internet's address space.
What's Actually Listening on Port 227?
On most systems: nothing.
To check what (if anything) is using port 227 on your machine:
On Linux/Mac:
On Windows:
Using netcat to test if the port responds:
Since this port is reserved and not assigned to any standard service, you probably won't find anything listening. But it's worth checking—sometimes non-standard software uses reserved ports, either accidentally or deliberately.
Why Reserved Ports Matter
Reserved ports are like margin space in a book. They give the system room to breathe, room to grow, room to handle something unexpected without having to reclaim already-assigned space.
The Internet is a living system. Protocols evolve. New needs emerge. Having blocks of reserved ports means IANA can respond to those needs without breaking existing assignments or forcing awkward re-numbering schemes.
Port 227 sits quietly in that reserved space, waiting for a purpose that may never come—or might arrive tomorrow.
Related Ports
The reserved block containing port 227:
- Ports 225-241 — Reserved by IANA (17 consecutive ports)
The ports surrounding this reserved block:
- Port 224 — masqdialer (TCP/UDP)
- Port 242 — direct (TCP/UDP)
Security Note
Since port 227 has no official assigned service, any traffic on this port should be treated with suspicion. If you see something listening on port 227, it's either:
- Custom software that chose an unused port (legitimate but non-standard)
- Malware trying to hide in an unassigned port (potentially malicious)
Always verify what's using unexpected ports on your system.
Frequently Asked Questions
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