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Port 686 (hcp-wismar)

IANA assigns port 686 to hcp-wismar: Hardware Control Protocol Wismar.

Well-known (system) port, 0-1023 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
hcp-wismar TCP Hardware Control Protocol Wismar David Merchant -
hcp-wismar UDP Hardware Control Protocol Wismar David Merchant -

Check what is listening on port 686

Linux: is anything listening on TCP 686?
sudo ss -tlnp 'sport = :686'
Linux: UDP 686
sudo ss -ulnp 'sport = :686'
Linux / macOS: which process owns the port
sudo lsof -nP -i :686
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':686 '
Windows (Command Prompt)
netstat -ano | findstr :686
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 686 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 686
From Windows
Test-NetConnection HOST -Port 686
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 686

Block port 686 in the firewall

ufw
sudo ufw deny 686/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 686 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 686 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 686' -Direction Inbound -Protocol TCP -LocalPort 686 -Action Block
ufw
sudo ufw deny 686/udp
iptables
sudo iptables -A INPUT -p udp --dport 686 -j DROP
nftables
sudo nft add rule inet filter input udp dport 686 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 686' -Direction Inbound -Protocol UDP -LocalPort 686 -Action Block

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