Port 1149: Blaze and bvtsonar — When one port serves two worlds

Port 1149 is registered twice with IANA—once for TCP, once for UDP. This isn't a mistake. It's how the port system works.

What Runs on Port 1149

TCP/1149: Blaze File Server¹ A file sharing service that uses port 1149 for TCP connections.

UDP/1149: bvtsonar (BlueView Sonar Service)² Communication protocol for BlueView imaging sonar systems—underwater sonar hardware used for marine imaging. The ProViewer software connects to BlueView sonar devices over UDP port 1149.

Why This Works

TCP and UDP are separate transport protocols. They maintain independent port namespaces. Port 1149 over TCP and port 1149 over UDP are completely different endpoints—like having the same house number on two different streets.

A packet arriving at port 1149 carries a flag: "I'm TCP" or "I'm UDP." The operating system routes it accordingly. No collision. No confusion.

This dual registration is common in the registered ports range. The same number can serve entirely different purposes as long as the protocols differ.

The Registered Ports Range

Port 1149 belongs to the registered ports range (1024-49151). These ports are assigned by IANA to specific services upon application. Unlike well-known ports (0-1023) which require root privileges, registered ports can be bound by regular user applications.

Anyone can request a registered port for their protocol. IANA reviews the application and assigns a number if the request is legitimate and the port is available. Blaze File Server and BlueView Sonar both went through this process.

Security Considerations

If you see unexpected traffic on port 1149:

Check what's listening:

# Linux/macOS
sudo lsof -i :1149
sudo netstat -tulpn | grep 1149

# Windows
netstat -ano | findstr :1149

Look at the protocol:

• TCP traffic might be Blaze File Server or something else using that port
• UDP traffic might be BlueView Sonar or another application

The registered range doesn't guarantee uniqueness in practice. Applications can bind to any port. Just because port 1149 is officially registered doesn't mean random software won't try to use it.

If you're running BlueView sonar equipment, your firewall needs to allow UDP/1149 for the ProViewer software to communicate with the hardware.³ If you're not running sonar equipment and see UDP traffic on 1149, investigate.

Why Unassigned Ports Matter

Not every port in the registered range has an official assignment. Most don't. The gaps exist for future services, experimental protocols, and private applications.

The structure matters more than the assignments. The port system provides 65,535 possible addresses per protocol (TCP and UDP each get their own set). Well-known ports (0-1023) handle critical infrastructure. Registered ports (1024-49151) serve specific applications. Dynamic ports (49152-65535) are free-for-all temporary addresses.

Port 1149 sitting in the registered range means: someone requested this, IANA approved it, and the assignment is documented. That's all. It doesn't mean the port is widely used or that nothing else will ever bind to it.

The Practical Reality

Most systems never see traffic on port 1149 unless they're running file sharing software or connected to underwater sonar hardware. The registration exists for the rare cases where those specific services need a standardized port number.

This is normal. The Internet has 65,535 ports per protocol. Most of them sit quiet most of the time. They're there when needed. That's enough.