Port 2641 (hdl-srv)

IANA assigns port 2641 to hdl-srv: HDL Server.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference

hdl-srv TCP HDL Server David Ely -

hdl-srv UDP HDL Server David Ely -

Linux: is anything listening on TCP 2641?

sudo ss -tlnp 'sport = :2641'

Linux: UDP 2641

sudo ss -ulnp 'sport = :2641'

Linux / macOS: which process owns the port

sudo lsof -nP -i :2641

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':2641 '

Windows (Command Prompt)

netstat -ano | findstr :2641

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 2641 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 2641

From Windows

Test-NetConnection HOST -Port 2641

UDP probe (no reply does not prove it is closed)

nc -vzu -w 5 HOST 2641

ufw

sudo ufw deny 2641/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 2641 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 2641 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 2641' -Direction Inbound -Protocol TCP -LocalPort 2641 -Action Block

ufw

sudo ufw deny 2641/udp

iptables

sudo iptables -A INPUT -p udp --dport 2641 -j DROP

nftables

sudo nft add rule inet filter input udp dport 2641 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block UDP 2641' -Direction Inbound -Protocol UDP -LocalPort 2641 -Action Block

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