Port 66 (sql-net, sql*net)

IANA assigns port 66 to sql-net, sql*net: Oracle SQL*NET IANA assigned this well-formed service name as a replacement for "sql*net"..

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

IANA assignment

Service nameProtoDescriptionAssigneeReference

sql-net TCP Oracle SQL*NET IANA assigned this well-formed service name as a replacement for "sql*net". Jack Haverty -

sql*net TCP Oracle SQL*NET
This entry is an alias to "sql-net". This entry is now historic, not usable for use with many common service discovery mechanisms. Jack Haverty -

sql-net UDP Oracle SQL*NET IANA assigned this well-formed service name as a replacement for "sql*net". Jack Haverty -

sql*net UDP Oracle SQL*NET
This entry is an alias to "sql-net". This entry is now historic, not usable for use with many common service discovery mechanisms. Jack Haverty -

Check what is listening on port 66

Linux: is anything listening on TCP 66?

sudo ss -tlnp 'sport = :66'

Linux: UDP 66

sudo ss -ulnp 'sport = :66'

Linux / macOS: which process owns the port

sudo lsof -nP -i :66

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':66 '

Windows (Command Prompt)

netstat -ano | findstr :66

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 66 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine

nc -vz -w 5 HOST 66

From Windows

Test-NetConnection HOST -Port 66

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

nc -vzu -w 5 HOST 66

Block port 66 in the firewall

ufw

sudo ufw deny 66/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 66 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 66 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 66' -Direction Inbound -Protocol TCP -LocalPort 66 -Action Block

ufw

sudo ufw deny 66/udp