Port 47808: BACnet
Port 47808 is BACnet, the standard protocol for building automation systems that control HVAC, lighting, and access control in commercial buildings. Exposing it to the internet has led to real incidents of building systems being manipulated remotely.
| Port number | 47808 |
|---|---|
| Service | BACnet building automation |
| Protocol | UDP |
| Category | IoT & automation |
| Default encryption | No |
How do I check whether port 47808 is open?
Port 47808 is UDP, which changes the answer: there is no handshake to complete, so nothing outside the host can prove the port is open. Asking the host itself is the reliable route.
| Question | Command | What to know |
|---|---|---|
| Is it open on a remote host? | sudo nmap -sU -p 47808 example.com | UDP has no handshake, so there is nothing to complete. nmap infers the state from whether an ICMP port-unreachable comes back, needs root, and is slow and easy to misread. A silent port may be open, filtered, or simply not replying to a probe it does not recognise. |
| What is listening locally? | ss -ulnp | grep ':47808 ' | Shows the UDP socket bound to port 47808. This is the reliable way to answer the question, because you are asking the host itself rather than guessing from outside. |
Replace example.com with the host you are testing. A blocked port and a port with nothing listening on it look identical from the outside, so if a service should be running, check locally before blaming the firewall.
Frequently asked questions
What is port 47808 used for?
Port 47808 is BACnet, the standard protocol for building automation systems that control HVAC, lighting, and access control in commercial buildings. Exposing it to the internet has led to real incidents of building systems being manipulated remotely.
Is port 47808 TCP or UDP?
Port 47808 (BACnet) uses UDP.
Is port 47808 secure?
Port 47808 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 47808 on my firewall?
Only if you specifically need BACnet. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.