Port 1900 (SSDP / UPnP)

Simple Service Discovery Protocol for UPnP device discovery (smart TVs, routers, media servers).

Registered (user) port, 1024-49151 UDP Network infrastructure Localhost or LAN only

Port 1900 is normally used over UDP; the checker tests TCP only, so a "filtered" result does not mean the UDP service is down.

What port 1900 is used for

Simple Service Discovery Protocol for UPnP device discovery (smart TVs, routers, media servers).

Security: should port 1900 be open?

Localhost or LAN only. Must not answer the internet: SSDP is a common DDoS reflection vector. Turn off UPnP on the router's WAN side; UPnP IGD also lets LAN malware open ports.

IANA assignment

Service nameProtoDescriptionAssigneeReference

ssdp TCP SSDP UPnP Forum -

ssdp UDP SSDP UPnP Forum -

Check what is listening on port 1900

Linux: UDP 1900

sudo ss -ulnp 'sport = :1900'

Linux / macOS: which process owns the port

sudo lsof -nP -i :1900

Windows (Command Prompt)

netstat -ano | findstr :1900

Windows (PowerShell)

Get-NetUDPEndpoint -LocalPort 1900

Test it from outside

UDP probe (no reply does not prove it is closed)

nc -vzu -w 5 HOST 1900

Block port 1900 in the firewall

ufw

sudo ufw deny 1900/udp

iptables

sudo iptables -A INPUT -p udp --dport 1900 -j DROP

nftables

sudo nft add rule inet filter input udp dport 1900 drop

Windows Firewall

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

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.