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Port 263 (hdap)

IANA assigns port 263 to hdap: HDAP.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
hdap TCP HDAP Troy Gau -
hdap UDP HDAP Troy Gau -

Check what is listening on port 263

Linux: is anything listening on TCP 263?
sudo ss -tlnp 'sport = :263'
Linux: UDP 263
sudo ss -ulnp 'sport = :263'
Linux / macOS: which process owns the port
sudo lsof -nP -i :263
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':263 '
Windows (Command Prompt)
netstat -ano | findstr :263
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 263 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 263
From Windows
Test-NetConnection HOST -Port 263
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 263

Block port 263 in the firewall

ufw
sudo ufw deny 263/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 263 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 263 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 263' -Direction Inbound -Protocol TCP -LocalPort 263 -Action Block
ufw
sudo ufw deny 263/udp
iptables
sudo iptables -A INPUT -p udp --dport 263 -j DROP
nftables
sudo nft add rule inet filter input udp dport 263 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 263' -Direction Inbound -Protocol UDP -LocalPort 263 -Action Block

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261nsiiops262arcisdms264bgmp265x-bone-ctl

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