Port 8081 (HTTP alternate (8081))

Secondary HTTP port, often for a second app, Nexus Repository, Metro (React Native) or a proxy's admin UI.

Registered (user) port, 1024-49151 TCP Web Expose only to trusted sources

What port 8081 is used for

Secondary HTTP port, often for a second app, Nexus Repository, Metro (React Native) or a proxy's admin UI.

Expose only to trusted sources. Check what is listening before opening it; it is typically an admin or development service.

Service nameProtoDescriptionAssigneeReference

sunproxyadmin TCP Sun Proxy Admin Service Arvind Srinivasan -

sunproxyadmin UDP Sun Proxy Admin Service Arvind Srinivasan -

Registry dates for this port: registered 2005-08.

Linux: is anything listening on TCP 8081?

sudo ss -tlnp 'sport = :8081'

Linux / macOS: which process owns the port

sudo lsof -nP -i :8081

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':8081 '

Windows (Command Prompt)

netstat -ano | findstr :8081

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 8081 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 8081

From Windows

Test-NetConnection HOST -Port 8081

Replace 203.0.113.10 with the address or network you trust. With ufw, make sure the default incoming policy is deny.

ufw (one trusted source)

sudo ufw allow from 203.0.113.10 to any port 8081 proto tcp

iptables

sudo iptables -A INPUT -p tcp --dport 8081 -s 203.0.113.10 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 8081 -j DROP

nftables

sudo nft add rule inet filter input ip saddr 203.0.113.10 tcp dport 8081 accept
sudo nft add rule inet filter input tcp dport 8081 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'TCP 8081 trusted' -Direction Inbound -Protocol TCP -LocalPort 8081 -RemoteAddress 203.0.113.10 -Action Allow

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