Port 210 (z39-50, z39.50)

IANA assigns port 210 to z39-50, z39.50: ANSI Z39.50 IANA assigned this well-formed service name as a replacement for "z39.50"..

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

IANA assignment

Service nameProtoDescriptionAssigneeReference

z39-50 TCP ANSI Z39.50 IANA assigned this well-formed service name as a replacement for "z39.50". Mark H Needleman -

z39.50 TCP ANSI Z39.50
This entry is an alias to "z39-50". This entry is now historic, not usable for use with many common service discovery mechanisms. Mark H Needleman -

z39-50 UDP ANSI Z39.50 IANA assigned this well-formed service name as a replacement for "z39.50". Mark H Needleman -

z39.50 UDP ANSI Z39.50
This entry is an alias to "z39-50". This entry is now historic, not usable for use with many common service discovery mechanisms. Mark H Needleman -

Check what is listening on port 210

Linux: is anything listening on TCP 210?

sudo ss -tlnp 'sport = :210'

Linux: UDP 210

sudo ss -ulnp 'sport = :210'

Linux / macOS: which process owns the port

sudo lsof -nP -i :210

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':210 '

Windows (Command Prompt)

netstat -ano | findstr :210

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 210 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine

nc -vz -w 5 HOST 210

From Windows

Test-NetConnection HOST -Port 210

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

nc -vzu -w 5 HOST 210

Block port 210 in the firewall

ufw

sudo ufw deny 210/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 210 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 210 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 210' -Direction Inbound -Protocol TCP -LocalPort 210 -Action Block

ufw

sudo ufw deny 210/udp