Port 1644: Unassigned — An empty slot in the registered range

Port 1644 has no official assignment from IANA. It's part of the registered port range (1024-49151), which means it's available for applications to claim, but nobody has formally registered it.

What the Registered Range Means

The Internet's 65,535 ports are divided into three ranges:

• Well-known ports (0-1023): Require root privileges, assigned to fundamental protocols
• Registered ports (1024-49151): Available for applications to register with IANA
• Dynamic/ephemeral ports (49152-65535): Used for temporary client-side connections

Port 1644 sits in the middle range. Any application can request to register it officially, but so far, no one has.¹

Unofficial Uses

While unassigned, port 1644 occasionally appears in use:

Internet Relay Chat (IRC): Some IRC servers use port 1644 as an alternate listening port. This is unofficial—the standard IRC ports are 6667 and nearby numbers (6660-6669), with 6697 for encrypted connections.²³ Port 1644 offers no particular advantage; it's just available space that some server administrators chose to use.

The reality: most ports in this range are like this. Applications pick a number that isn't obviously taken and use it. Sometimes it gets documented in port databases. Usually it doesn't.

Why Unassigned Ports Matter

The registered range exists because not every network service needs to be universally standardized. Your internal application doesn't need IANA approval to listen on port 1644. You just need to make sure nothing else on your system is using it.

This flexibility is the point. Well-known ports below 1024 are reserved for protocols everyone needs to agree on—HTTP, SSH, DNS. Registered ports are for everything else. Some get formally registered. Most just get used.

Checking What's Listening

To see if anything is using port 1644 on your system:

Linux/macOS:

sudo lsof -i :1644
netstat -an | grep 1644

Windows:

netstat -ano | findstr :1644

If something is listening, these commands will show you what process owns the port. If nothing appears, the port is available.

The Nature of Empty Space

Port 1644 represents most of the port space—unclaimed, undocumented, waiting. The well-known ports get all the attention because they carry the protocols that make the Internet work. But the registered range is where most applications actually live. They don't need ceremony. They just need a number.

If you're running a service that needs a port, 1644 is as good as any. Just document what you're using it for, so the next person who looks doesn't have to guess.

Related Ports

• Port 194: The original IANA-assigned port for IRC (rarely used)
• Ports 6667-6669: Standard IRC server ports
• Port 6697: IRC over TLS/SSL³