Port 102 (Siemens S7 (ISO-TSAP))

ISO transport over TCP (RFC 1006), used by Siemens S7 PLCs and some Microsoft Exchange X.400 setups.

Well-known (system) port, 0-1023 TCP Industrial control (ICS/SCADA) Do not expose to the internet

What port 102 is used for

ISO transport over TCP (RFC 1006), used by Siemens S7 PLCs and some Microsoft Exchange X.400 setups.

Do not expose to the internet. Exposed S7 PLCs can be stopped and reprogrammed; Stuxnet targeted S7 systems. Keep OT networks isolated.

Service nameProtoDescriptionAssigneeReference

iso-tsap TCP ISO-TSAP Class 0 Marshall Rose -

iso-tsap UDP ISO-TSAP Class 0 Marshall Rose -

Linux: is anything listening on TCP 102?

sudo ss -tlnp 'sport = :102'

Linux / macOS: which process owns the port

sudo lsof -nP -i :102

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':102 '

Windows (Command Prompt)

netstat -ano | findstr :102

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 102 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 102

From Windows

Test-NetConnection HOST -Port 102

ufw

sudo ufw deny 102/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 102 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 102 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 102' -Direction Inbound -Protocol TCP -LocalPort 102 -Action Block

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