Port 304 has no official assignment. It belongs to the well-known ports range (0-1023), the address space reserved for the Internet's most essential services, but IANA has never designated a service for this port.1
What "Unassigned" Means
The Internet Assigned Numbers Authority maintains three categories of port status: Assigned, Reserved, and Unassigned. Port 304 falls into the third category—available for assignment if someone requests it through the proper procedures.2
When RFC 6335 documented the state of port assignments, approximately 76% of well-known ports had been assigned to services. The remaining 24%, including port 304, sit empty. Not every number needs a purpose.
The Well-Known Ports Range
Well-known ports (0-1023) are also called system ports. They require root privileges to bind to on Unix-like systems. This restriction exists because these ports were intended for standard Internet services—the protocols that make the Internet work.
Port 22 carries SSH. Port 80 carries HTTP. Port 443 carries HTTPS. Port 304 carries nothing.
The restriction means that on most systems, only privileged processes can listen on port 304. This doesn't stop it from being empty—it just means that if something ever used it, that something would need administrative access.
Why Unassigned Ports Matter
Unassigned ports serve two purposes: they're available for future protocols, and they represent restraint. Not every idea needs a dedicated port number. The Internet has 65,536 ports per protocol, but that doesn't mean we should fill them all.
Port 304 could be assigned tomorrow if someone designed a protocol significant enough to warrant a well-known port number. The application process exists. But for now, it waits.
Checking What's Listening
Even though port 304 has no official assignment, something on your system could be using it. Software doesn't need IANA's permission to listen on a port—the registry is documentation, not enforcement.
On Linux or macOS, check what's listening on port 304:
Or using netstat:
On Windows, use netstat:
If nothing returns, the port is unused. If something does return, you've found unofficial use—software that chose this port without an official assignment.3
The Honest Reality
Port 304 has no story because it has no service. No RFC defines its purpose. No protocol depends on it. No administrator monitors it. It's a number in a registry, nothing more.
Some unassigned ports develop informal uses—software that picks a number and hopes for no conflicts. Port 304 doesn't appear in common trojan port lists or unofficial service databases. It's not just unassigned; it's genuinely unused.
This is fine. Not every port needs a purpose. The gaps in the registry are as important as the assignments—they represent space for the Internet to grow, or simply space that never needs filling.
Port 304 is available. It's been available for decades. It may stay available forever.
Related Ports
The well-known ports range (0-1023) contains both heavily used ports and empty spaces like port 304. Nearby assigned ports include port 308 (Novastor Backup), though many ports in this range remain unassigned.
Frequently Asked Questions
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