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Port 5265 (3com-njack-2)

IANA assigns port 5265 to 3com-njack-2: 3Com Network Jack Port 2.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
3com-njack-2 TCP 3Com Network Jack Port 2 Abhay Rajaram -
3com-njack-2 UDP 3Com Network Jack Port 2 Abhay Rajaram -

Registry dates for this port: registered 2003-03.

Check what is listening on port 5265

Linux: is anything listening on TCP 5265?
sudo ss -tlnp 'sport = :5265'
Linux: UDP 5265
sudo ss -ulnp 'sport = :5265'
Linux / macOS: which process owns the port
sudo lsof -nP -i :5265
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':5265 '
Windows (Command Prompt)
netstat -ano | findstr :5265
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 5265 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 5265
From Windows
Test-NetConnection HOST -Port 5265
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 5265

Block port 5265 in the firewall

ufw
sudo ufw deny 5265/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 5265 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 5265 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 5265' -Direction Inbound -Protocol TCP -LocalPort 5265 -Action Block
ufw
sudo ufw deny 5265/udp
iptables
sudo iptables -A INPUT -p udp --dport 5265 -j DROP
nftables
sudo nft add rule inet filter input udp dport 5265 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 5265' -Direction Inbound -Protocol UDP -LocalPort 5265 -Action Block

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