Port 583 sits in the IANA registry with an official assignment: philips-vc, short for Philips Video-Conferencing. Both TCP and UDP on port 583 were reserved for this proprietary video conferencing system.1
The system is obsolete. Philips no longer manufactures or supports whatever video conferencing product once used this port. But the reservation remains.
What the Well-Known Range Means
Port 583 falls in the well-known ports range (0-1023), which means its assignment required IANA approval and is considered a system port. These ports are typically reserved for standardized services that need consistent port numbers across all systems.
The fact that port 583 was assigned in this privileged range suggests that at the time of assignment, Philips Video-Conferencing was expected to be a significant, widely-deployed service that would benefit from a reserved port number.
That didn't happen. The technology came and went.
The Reality of Obsolete Assignments
Port 583 represents something common in the IANA registry: technological optimism frozen in time. When a company or standards body requests a port assignment, they're making a bet that their protocol will matter enough to justify reserving a number forever. Sometimes that bet pays off (SSH on port 22, HTTPS on port 443). Sometimes it doesn't.
The registry is full of ports assigned to services that no one uses anymore. They sit there, marked as taken, while the world moves on to different protocols and different solutions. Video conferencing today happens over WebRTC, Zoom's proprietary protocols, Microsoft Teams—not over a Philips system from decades ago.
What You'll Actually Find on Port 583
In practice, port 583 is almost never used. You might find:
- Nothing — The most common case. The port sits closed.
- Security scanners — Automated tools probing for any open port
- Accidental usage — Some application or service configured to use 583 without knowing about the official assignment
- Proprietary systems — Organizations that decided to repurpose the port for internal services, knowing the original assignment is obsolete
Checking What's Listening
To see if anything is actually using port 583 on your system:
Linux/macOS:
Windows:
Most likely, you'll find nothing. Port 583 is a reservation without a tenant.
Why Obsolete Ports Matter
Port 583 illustrates a challenge in Internet infrastructure: assignments are essentially permanent. Once a port is officially assigned, removing that assignment is difficult. The registry needs to maintain historical accuracy, and there's always a risk that someone, somewhere, is still running that old system.
So ports accumulate. The registry fills with assignments to services that died years ago. Every obsolete port is one fewer number available for new protocols that might actually need it.
The well-known ports range (0-1023) is particularly precious because there are only 1,024 numbers. When one is assigned to a technology that fades away, that's real opportunity cost.
The Lesson
Port 583 is a small reminder that the Internet's infrastructure is built on decisions made decades ago, some of which turned out to be wrong. We live with those decisions because changing them is harder than leaving them alone.
Somewhere in the IANA registry, port 583 still belongs to Philips Video-Conferencing. The entry will probably remain there long after everyone who worked on that system has retired.
The port is waiting for a service that's never coming back.
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