HTTPfy

Port 3874 (sixxsconfig)

IANA assigns port 3874 to sixxsconfig: SixXS Configuration.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
sixxsconfig TCP SixXS Configuration Jeroen Massar -
sixxsconfig UDP SixXS Configuration Jeroen Massar -

Registry dates for this port: registered 2003-11.

Check what is listening on port 3874

Linux: is anything listening on TCP 3874?
sudo ss -tlnp 'sport = :3874'
Linux: UDP 3874
sudo ss -ulnp 'sport = :3874'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3874
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3874 '
Windows (Command Prompt)
netstat -ano | findstr :3874
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3874 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3874
From Windows
Test-NetConnection HOST -Port 3874
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3874

Block port 3874 in the firewall

ufw
sudo ufw deny 3874/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3874 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3874 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3874' -Direction Inbound -Protocol TCP -LocalPort 3874 -Action Block
ufw
sudo ufw deny 3874/udp
iptables
sudo iptables -A INPUT -p udp --dport 3874 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3874 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3874' -Direction Inbound -Protocol UDP -LocalPort 3874 -Action Block

Related ports

3872oem-agent3873fagordnc3875pnbscada3876dl-agent, dl_agent

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