Before the World Wide Web. Before browsers. Before HTTP and HTML. There was videotex.
Port 516 carries the videotex protocol — a system for accessing text and graphics over telephone lines that brought millions of people online in the 1980s, long before most people had heard the word "Internet."1
In France, it was called Minitel. It was everywhere. And it ran on this port.
What Videotex Was
Videotex was interactive information delivery over phone lines, displayed on dedicated terminals or modified televisions.2 You dialed in. The screen showed text and simple graphics. You navigated with a keypad. You could check train schedules, book tickets, send messages, read news, or access thousands of services.
It was the Internet before the Internet existed as a mass phenomenon.
The technology appeared in multiple countries with different names: Prestel in the United Kingdom (launched 1979), Minitel in France (1982), Telidon in Canada. Each system had its own protocol specifications — CCITT Recommendation S.100, ANSI X3.110, proprietary Bell System standards.3
Port 516 was assigned by IANA to support these videotex services.4
The French Revolution
France Telecom made a decision that changed everything: they gave the terminals away for free.5
The reason was practical, not visionary. Printing and shipping millions of phone books every year was expensive. A free terminal that could display the phone directory electronically was cheaper. But once millions of homes had terminals sitting next to their telephones, something unexpected happened.
People started building services. By 1990, tens of millions of Minitel terminals were in use across France. You could bank, shop, chat, flirt, book travel, check the weather, access government services — all through a beige terminal with a tiny screen and a phone line.6
It worked. For years. The last Minitel server shut down in 2012.
What Made It Different
Videotex wasn't the Internet. The protocols were incompatible. The network was centralized. The terminals were closed systems. But it worked at scale, and it worked before TCP/IP became the standard that unified everything.
The protocol used geometric primitives to draw graphics — points, lines, arcs, rectangles, polygons.3 Efficient enough to work over phone lines that could barely manage a few hundred bits per second.
In Britain, Prestel never achieved the same adoption — partly because users had to pay for the terminal, a monthly service fee, and phone charges. It peaked at 90,000 subscribers.5
In France, free terminals removed the barrier. Millions of people went online.
Why It Matters
Port 516 is a museum. The videotex URI scheme is marked "historical" in IANA's registry, last updated in 2008.4 RFC 2122 introduced the VEMMI protocol (port 575) to replace it.4
But this port represents something real: the first time ordinary people, not researchers or engineers, went online in significant numbers. They didn't know what TCP/IP was. They didn't care. They had a terminal, a phone line, and services they wanted to use.
The Web came later and replaced it all. But before HTTP conquered the world, millions of people were already online, navigating through menus and typing on keypads.
Port 516 carried that world.
Security Considerations
Videotex is obsolete. If you find something listening on port 516 today, it's either:
- A historical system kept running for archival purposes
- A hobbyist recreation of old videotex services
- Something else entirely, using an abandoned port number
The protocol predates modern security practices. Don't use it for anything that matters.
Related Ports
- Port 575 — VEMMI, the protocol designed to replace videotex
- Port 23 — Telnet, another terminal protocol from the same era
- Port 3389 — RDP, modern remote terminal access
Checking Port 516
To see if anything is listening on port 516:
To test connectivity:
Common Questions
Is videotex still used?
No. The last major videotex system (France's Minitel) shut down in 2012. Some hobbyist and archival projects keep the technology alive, but it has no commercial presence.
What replaced videotex?
The World Wide Web. HTTP, HTML, and graphical web browsers provided everything videotex offered and more — with open standards, global reach, and no need for specialized terminals.
Why did France's Minitel succeed when others failed?
Free terminals. In countries where users had to buy hardware and pay subscription fees, adoption remained low. France Telecom distributed millions of free terminals, creating a network effect that sustained the service for decades.
Can I still access videotex services?
A few enthusiast projects recreate videotex experiences for historical and educational purposes. The original commercial networks are gone.
What does "historical" status mean in IANA's registry?
It means the protocol is no longer in active use and exists primarily for historical reference. The URI scheme and port assignment remain documented but are not recommended for new implementations.
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