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Port 6791 (hnm)

IANA assigns port 6791 to hnm: Halcyon Network Manager.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
hnm TCP Halcyon Network Manager Fortra -
hnm UDP Halcyon Network Manager Fortra -

Registry dates for this port: registered 2005-05, last modified 2023-05-24.

Check what is listening on port 6791

Linux: is anything listening on TCP 6791?
sudo ss -tlnp 'sport = :6791'
Linux: UDP 6791
sudo ss -ulnp 'sport = :6791'
Linux / macOS: which process owns the port
sudo lsof -nP -i :6791
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':6791 '
Windows (Command Prompt)
netstat -ano | findstr :6791
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 6791 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 6791
From Windows
Test-NetConnection HOST -Port 6791
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 6791

Block port 6791 in the firewall

ufw
sudo ufw deny 6791/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 6791 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 6791 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 6791' -Direction Inbound -Protocol TCP -LocalPort 6791 -Action Block
ufw
sudo ufw deny 6791/udp
iptables
sudo iptables -A INPUT -p udp --dport 6791 -j DROP
nftables
sudo nft add rule inet filter input udp dport 6791 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 6791' -Direction Inbound -Protocol UDP -LocalPort 6791 -Action Block

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