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Port 2391 (3com-net-mgmt)

IANA assigns port 2391 to 3com-net-mgmt: 3COM Net Management.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
3com-net-mgmt TCP 3COM Net Management Prathibha Nagvar -
3com-net-mgmt UDP 3COM Net Management Prathibha Nagvar -

Check what is listening on port 2391

Linux: is anything listening on TCP 2391?
sudo ss -tlnp 'sport = :2391'
Linux: UDP 2391
sudo ss -ulnp 'sport = :2391'
Linux / macOS: which process owns the port
sudo lsof -nP -i :2391
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':2391 '
Windows (Command Prompt)
netstat -ano | findstr :2391
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 2391 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 2391
From Windows
Test-NetConnection HOST -Port 2391
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 2391

Block port 2391 in the firewall

ufw
sudo ufw deny 2391/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 2391 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 2391 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 2391' -Direction Inbound -Protocol TCP -LocalPort 2391 -Action Block
ufw
sudo ufw deny 2391/udp
iptables
sudo iptables -A INPUT -p udp --dport 2391 -j DROP
nftables
sudo nft add rule inet filter input udp dport 2391 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 2391' -Direction Inbound -Protocol UDP -LocalPort 2391 -Action Block

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