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Port 3784 (bfd-control)

IANA assigns port 3784 to bfd-control: BFD Control Protocol.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
bfd-control TCP BFD Control Protocol - RFC 5881
bfd-control UDP BFD Control Protocol - RFC 5881

Check what is listening on port 3784

Linux: is anything listening on TCP 3784?
sudo ss -tlnp 'sport = :3784'
Linux: UDP 3784
sudo ss -ulnp 'sport = :3784'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3784
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3784 '
Windows (Command Prompt)
netstat -ano | findstr :3784
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3784 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3784
From Windows
Test-NetConnection HOST -Port 3784
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3784

Block port 3784 in the firewall

ufw
sudo ufw deny 3784/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3784 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3784 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3784' -Direction Inbound -Protocol TCP -LocalPort 3784 -Action Block
ufw
sudo ufw deny 3784/udp
iptables
sudo iptables -A INPUT -p udp --dport 3784 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3784 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3784' -Direction Inbound -Protocol UDP -LocalPort 3784 -Action Block

Related ports

3782iso-tp0s3783bim-pem3785bfd-echo3786upstriggervsw

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