Port 1673 is registered with IANA for Intel ProShare Multicast (proshare-mc-1), part of a videoconferencing system Intel launched in 1994. The product is dead. The port registration remains.
What ProShare Was
In January 1994, Intel unveiled ProShare — a $2,499 package (camera and headset included) that let two people video call each other while simultaneously editing the same document. Real-time collaborative video on a desktop PC, thirty years ago.
It was genuinely ambitious. Astronauts on Space Shuttle Endeavour used ProShare in 1995 to share photos with ground control in Houston. Intel poured $750 million and five years of work from 700 engineers into the platform.
It failed. Not because the technology was wrong, but because the phone companies refused to build the infrastructure it needed. ProShare depended on ISDN lines — a digital telephone standard that would have given homes broadband-grade connectivity. The major telcos never deployed it at scale. Without the pipes, the platform couldn't reach the people it was built for.
Intel abandoned ProShare in the late 1990s. The port numbers stayed behind.
The Port Range
Port 1673 sits in the registered port range (1024–49151). These ports are not pre-assigned by the operating system — they require something to deliberately open them. Applications register these ports with IANA to signal "this is mine," preventing conflicts with other software.
Adjacent port 1674 is registered as proshare-mc-2, the second ProShare multicast channel. The two ports traveled together.
Is Anything Using This Port Today?
Almost certainly not ProShare. If you see traffic on port 1673, something else has opened it — intentionally or not.
On Linux/macOS:
On Windows:
If you find a process you don't recognize, check it. An unassigned port with active traffic is worth investigating.
Why This Port Still Matters
Port 1673 is a small lesson in how the registry actually works. IANA assigns ports to products and services, not concepts. When the product dies, the port doesn't get cleaned up — it sits in the registry, labeled, unclaimed in practice but technically spoken for.
The registered range has thousands of these fossils. Products that failed. Protocols that were superseded. Services that no one runs anymore but that technically retain their reservation. The registry is partly a living directory and partly a graveyard.
That's not a flaw. It's a feature. Port conflicts cause real problems, and an abandoned registration costs nothing while preventing a future developer from accidentally squatting on a number that might, in some network somewhere, still carry old traffic.
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