HTTPfy

Port 9131 (dddp)

IANA assigns port 9131 to dddp: Dynamic Device Discovery.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
dddp TCP Dynamic Device Discovery Shane Dick -
dddp UDP Dynamic Device Discovery Shane Dick -

Registry dates for this port: registered 2005-08.

Check what is listening on port 9131

Linux: is anything listening on TCP 9131?
sudo ss -tlnp 'sport = :9131'
Linux: UDP 9131
sudo ss -ulnp 'sport = :9131'
Linux / macOS: which process owns the port
sudo lsof -nP -i :9131
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':9131 '
Windows (Command Prompt)
netstat -ano | findstr :9131
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 9131 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 9131
From Windows
Test-NetConnection HOST -Port 9131
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 9131

Block port 9131 in the firewall

ufw
sudo ufw deny 9131/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 9131 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 9131 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 9131' -Direction Inbound -Protocol TCP -LocalPort 9131 -Action Block
ufw
sudo ufw deny 9131/udp
iptables
sudo iptables -A INPUT -p udp --dport 9131 -j DROP
nftables
sudo nft add rule inet filter input udp dport 9131 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 9131' -Direction Inbound -Protocol UDP -LocalPort 9131 -Action Block

Related ports

9122grcmp9123grcp9160apani19161apani2

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.