Port 1900: SSDP
Port 1900 is SSDP, the discovery protocol behind UPnP that lets devices like smart TVs, printers, and media servers announce themselves and find each other on the local network. It is not meant to be reachable from outside the LAN.
| Port number | 1900 |
|---|---|
| Service | Simple Service Discovery Protocol |
| Protocol | UDP |
| Category | Chat & messaging |
| Default encryption | No |
How do I check whether port 1900 is open?
Port 1900 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 1900 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 ':1900 ' | Shows the UDP socket bound to port 1900. 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 1900 used for?
Port 1900 is SSDP, the discovery protocol behind UPnP that lets devices like smart TVs, printers, and media servers announce themselves and find each other on the local network. It is not meant to be reachable from outside the LAN.
Is port 1900 TCP or UDP?
Port 1900 (SSDP) uses UDP.
Is port 1900 secure?
Port 1900 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 1900 on my firewall?
Only if you specifically need SSDP. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.