ONVIF discovery
ONVIF Discovery Port 3702
ONVIF camera discovery is built on WS-Discovery. In practice, your viewer sends a probe on UDP port 3702 to multicast address 239.255.255.250, then cameras answer with their device service address.
Quick answer
IPv4 multicast: 239.255.255.250
Discovery port: 3702
Protocol: WS-Discovery / SOAP-over-UDP
Scope: usually the local subnet
What SmartRTSP does during ONVIF scan
When you tap Scan, SmartRTSP searches the local network for ONVIF devices, reads the camera service endpoint, then asks the camera for its stream profile and RTSP URL. That is why ONVIF discovery can find a camera even when you do not know the exact RTSP path.
Why all-subnet ONVIF discovery often fails
Queries like "all subnet ONVIF" usually point to a network boundary problem. WS-Discovery multicast is normally local network traffic. It may not cross VLANs, guest Wi-Fi, mesh isolation, VPN tunnels, or routers unless multicast routing is explicitly configured.
- Put the phone, iPad, Mac, or Apple TV on the same Wi-Fi/VLAN as the camera.
- Disable guest-network isolation while testing.
- Allow UDP 3702 and camera HTTP/HTTPS management ports on the local firewall.
- If the camera is on another subnet, add it manually by IP address and RTSP URL.
Troubleshooting checklist
Camera does not appear
Confirm ONVIF is enabled in the camera web UI and that a separate ONVIF user exists if the brand requires it.
Discovery works, stream fails
The ONVIF service may be reachable while RTSP port 554 is blocked. Test the RTSP URL separately.
Multiple NICs on Mac
VPN, Ethernet and Wi-Fi can confuse multicast routing. Try one active network interface during scan.
NVR channels missing
Some recorders expose cameras as channel streams instead of separate ONVIF devices. Use the NVR RTSP channel URL.
Official references
For protocol-level confirmation, see the ONVIF test specifications for WS-Discovery behavior, the OASIS WS-Discovery specification, and IETF/IANA references for RTSP port 554.