HTTPfy

Port 281 (personal-link)

IANA assigns port 281 to personal-link: Personal Link.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
personal-link TCP Personal Link Dan Cummings -
personal-link UDP Personal Link Dan Cummings -

Check what is listening on port 281

Linux: is anything listening on TCP 281?
sudo ss -tlnp 'sport = :281'
Linux: UDP 281
sudo ss -ulnp 'sport = :281'
Linux / macOS: which process owns the port
sudo lsof -nP -i :281
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':281 '
Windows (Command Prompt)
netstat -ano | findstr :281
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 281 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 281
From Windows
Test-NetConnection HOST -Port 281
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 281

Block port 281 in the firewall

ufw
sudo ufw deny 281/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 281 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 281 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 281' -Direction Inbound -Protocol TCP -LocalPort 281 -Action Block
ufw
sudo ufw deny 281/udp
iptables
sudo iptables -A INPUT -p udp --dport 281 -j DROP
nftables
sudo nft add rule inet filter input udp dport 281 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 281' -Direction Inbound -Protocol UDP -LocalPort 281 -Action Block

Related ports

271pt-tls280http-mgmt282cableport-ax283rescap

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