Port 732: Unassigned — An Empty Space in the Well-Known Range

Port 732 is unassigned. According to IANA's official registry, both TCP and UDP on port 732 have no designated service.¹²

What This Means

Port 732 falls in the well-known port range (0-1023). These ports were originally reserved for system services—things like HTTP on 80, HTTPS on 443, SSH on 22. IANA manages this range carefully. You can't just claim a well-known port for your application. It requires IETF review or IESG approval.³

But port 732 was never claimed. It's been sitting empty for decades.

Why Unassigned Ports Exist

The well-known range has 1,024 ports (0-1023). Not all of them are used. When the port system was designed in the early days of the Internet, the architects set aside this range for important services. But they couldn't predict which services those would be.

Some ports got assigned immediately—FTP, Telnet, SMTP. Others were claimed later as new protocols emerged. And some, like port 732, were just never needed.

It's not a problem. It's just empty space.

Could Port 732 Be Used for Something?

Technically, yes. Any application could listen on port 732. There's no law against it. But there are good reasons not to:

Collision risk — If two different applications both decide to use port 732, they'll conflict. Imagine two services on the same machine both trying to bind to the same port. One fails.

No official recognition — Without an IANA assignment, port 732 has no meaning. Other systems won't know what to expect. Firewalls won't have rules for it. Documentation won't reference it.

Better alternatives exist — The registered port range (1024-49151) is designed for applications that need consistent port numbers but don't qualify for well-known status. That's the appropriate place for custom services.

How to Check What's Listening on Port 732

Even though port 732 is unassigned, something on your system could still be using it. Here's how to check:

On Linux or macOS:

sudo lsof -i :732

Or:

sudo netstat -tlnp | grep :732

On Windows:

netstat -ano | findstr :732

If nothing returns, the port is unused. If something does return, you'll see which process is listening.

The Gap in the Map

Port 732 is one of hundreds of unassigned ports in the well-known range. They're gaps in the Internet's numbering system—numbers that were reserved but never claimed.¹

These gaps don't hurt anything. They're just quiet. No packets flow through them. No services announce themselves. They exist in case someone, someday, needs them.

Maybe port 732 will stay empty forever. Maybe in 2045, someone will write an RFC proposing a new protocol that needs it. Either way, it waits.

The Internet has room for things that don't exist yet.