HTTPfy

Port 3991 (bv-smcsrv)

IANA assigns port 3991 to bv-smcsrv: BindView-SMCServer.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
bv-smcsrv TCP BindView-SMCServer - -
bv-smcsrv UDP BindView-SMCServer - -

Check what is listening on port 3991

Linux: is anything listening on TCP 3991?
sudo ss -tlnp 'sport = :3991'
Linux: UDP 3991
sudo ss -ulnp 'sport = :3991'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3991
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3991 '
Windows (Command Prompt)
netstat -ano | findstr :3991
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3991 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3991
From Windows
Test-NetConnection HOST -Port 3991
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3991

Block port 3991 in the firewall

ufw
sudo ufw deny 3991/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3991 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3991 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3991' -Direction Inbound -Protocol TCP -LocalPort 3991 -Action Block
ufw
sudo ufw deny 3991/udp
iptables
sudo iptables -A INPUT -p udp --dport 3991 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3991 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3991' -Direction Inbound -Protocol UDP -LocalPort 3991 -Action Block

Related ports

3989bv-queryengine3990bv-is3992bv-ds3993bv-agent

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