Port 1536: AMPR-Inter — Where Amateur Radio Meets the Internet

Port 1536 is registered with IANA for ampr-inter (Amateur Packet Radio Network - Inter), a service that lets amateur radio operators connect their packet radio networks across the Internet.¹

What This Port Does

Amateur radio operators—ham radio enthusiasts—run digital networks over radio frequencies using packet radio. These networks need to talk to each other across long distances. Port 1536 is how they do it over the Internet.

When two amateur radio networks want to communicate, they use ampr-inter on port 1536 to bridge the connection. The radio waves carry data locally, and the Internet carries it between distant networks.

The AMPRNet

This port exists because of AMPRNet (Amateur Packet Radio Network), a TCP/IP network reserved specifically for licensed amateur radio operators. AMPRNet uses IP addresses in the 44.0.0.0/8 range—a whole chunk of Internet address space set aside for ham radio.²

Port 1536 is part of that infrastructure. It's how AMPRNet nodes talk to each other when they're not connected by radio.

Who Uses This

You'll only encounter this port if:

• You're a licensed amateur radio operator running packet radio
• You're connecting amateur radio networks across the Internet
• You're troubleshooting traffic on a network that includes ham radio equipment

For everyone else, this port sits unused. And that's fine. Not every port needs to carry millions of connections. Some exist for small communities doing specific things.

The Registered Ports Range

Port 1536 falls in the registered ports range (1024-49151). These ports are registered with IANA for specific services, but they're not as universally critical as well-known ports like 80 or 443.

Registered ports are:

• Assigned to specific applications or protocols
• Documented in the IANA registry
• Available for anyone to use, but officially claimed for particular purposes

Security Considerations

Like any registered port, 1536 can be used for things other than its intended purpose. Some sources mention that malware has occasionally used this port,³ but the port number alone doesn't prove anything.

If you see unexpected traffic on port 1536 and you're not running amateur radio equipment, investigate:

# Check what's listening on port 1536
sudo lsof -i :1536

# Or on Linux
sudo netstat -tulpn | grep 1536

If something's listening and you don't know why, find out what it is before assuming it's malicious.

Why This Port Matters

Port 1536 exists because amateur radio operators needed a way to extend their networks beyond radio range. Someone saw that need, registered the port, and built the infrastructure.

Most people will never use it. But for the small community of ham radio enthusiasts running packet radio networks, this port is essential. It's the bridge between radio waves and Internet packets.

That's what ports are for: giving every protocol, every community, every use case a place to exist without collision.