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Port 9668 (tec5-sdctp)

IANA assigns port 9668 to tec5-sdctp: tec5 Spectral Device Control Protocol.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
tec5-sdctp TCP tec5 Spectral Device Control Protocol Michael Muth -
tec5-sdctp UDP tec5 Spectral Device Control Protocol Michael Muth -

Registry dates for this port: registered 2009-05-11.

Check what is listening on port 9668

Linux: is anything listening on TCP 9668?
sudo ss -tlnp 'sport = :9668'
Linux: UDP 9668
sudo ss -ulnp 'sport = :9668'
Linux / macOS: which process owns the port
sudo lsof -nP -i :9668
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':9668 '
Windows (Command Prompt)
netstat -ano | findstr :9668
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 9668 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 9668
From Windows
Test-NetConnection HOST -Port 9668
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 9668

Block port 9668 in the firewall

ufw
sudo ufw deny 9668/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 9668 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 9668 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 9668' -Direction Inbound -Protocol TCP -LocalPort 9668 -Action Block
ufw
sudo ufw deny 9668/udp
iptables
sudo iptables -A INPUT -p udp --dport 9668 -j DROP
nftables
sudo nft add rule inet filter input udp dport 9668 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 9668' -Direction Inbound -Protocol UDP -LocalPort 9668 -Action Block

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