NetSecWallFree trialDownload
Port 1900 · UDP

Port 1900: SSDP (UPnP discovery)

Simple Service Discovery Protocol: how Windows, media apps and browsers find smart TVs, media servers and routers on the local network, over the multicast address 239.255.255.250.

Protocol
UDP
On Windows
svchost.exe (SSDP Discovery service, SSDPSRV)
Risk if open to the internet
High

Seeing it on your PC

svchost.exe, a browser or a media app on 1900 is looking for devices. Normal with network discovery turned on.

Should you block it?

Fine on a local network. Never expose it to the internet: open SSDP is used to amplify denial-of-service attacks. Turning off network discovery on public networks stops it there.

Check it on your PC

Run this in PowerShell to see what is using port 1900 right now, and which program owns it:

Get-NetUDPEndpoint -LocalPort 1900 -ErrorAction SilentlyContinue | Select-Object LocalAddress,LocalPort,@{n='Process';e={(Get-Process -Id $_.OwningProcess -ErrorAction SilentlyContinue).ProcessName}}

No output means nothing is using the port at the moment. For every connection at once, paste netstat -ano into the netstat explainer.

Block it in Windows Firewall

In PowerShell run as administrator, this stops other computers from connecting to this port on your PC. It does not stop your own programs connecting out.

New-NetFirewallRule -DisplayName "Block inbound UDP 1900" -Direction Inbound -Protocol UDP -LocalPort 1900 -Action Block

Undo it with Remove-NetFirewallRule -DisplayName "Block inbound …", using the same name. If you depend on the service on your local network, this rule stops that too.