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Port 38 (rap)

IANA assigns port 38 to rap: Route Access Protocol.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
rap TCP Route Access Protocol Robert Ullmann -
rap UDP Route Access Protocol Robert Ullmann -

Check what is listening on port 38

Linux: is anything listening on TCP 38?
sudo ss -tlnp 'sport = :38'
Linux: UDP 38
sudo ss -ulnp 'sport = :38'
Linux / macOS: which process owns the port
sudo lsof -nP -i :38
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':38 '
Windows (Command Prompt)
netstat -ano | findstr :38
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 38 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 38
From Windows
Test-NetConnection HOST -Port 38
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 38

Block port 38 in the firewall

ufw
sudo ufw deny 38/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 38 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 38 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 38' -Direction Inbound -Protocol TCP -LocalPort 38 -Action Block
ufw
sudo ufw deny 38/udp
iptables
sudo iptables -A INPUT -p udp --dport 38 -j DROP
nftables
sudo nft add rule inet filter input udp dport 38 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 38' -Direction Inbound -Protocol UDP -LocalPort 38 -Action Block

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