Port 49152: Dynamic port range start
Port 49152 is the first port in the dynamic range, used for temporary connections and by many UPnP devices.
What runs on port 49152
IANA reserves 49152 to 65535 for dynamic or private use, and modern Windows and macOS pick outgoing connection ports from this range. Windows also hands out RPC service ports here. The libupnp library that many UPnP devices are built on starts its web server at 49152 by default.
On a home network
Routers, smart TVs, media servers and smart plugs often serve their UPnP device description on 49152 or a neighbouring port. Windows PCs show RPC services on high ports in this range.
If port 49152 is reachable from the internet
On the LAN this is normal. From the internet, a UPnP web service on 49152 is a problem: UPnP was never meant to face the internet, and some implementations let outsiders read device details or change port mappings. Windows RPC ports in this range should also stay internal.
How to check whether it is open on your network
A LAN port scan that finds 49152 on a TV or router usually means UPnP. Disabling UPnP on the router, or at least reviewing its mapping table, stops devices from opening ports to the outside by themselves.
To find out whether port 49152 is open on something in your home, and whether the internet can reach it, the app scans your Wi-Fi from your phone and checks your public address from the outside. It says what it checked and what it could not. Get RECON for iPhone — one-time purchase, no account, nothing leaves the device.