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Port 527 (stx)

IANA assigns port 527 to stx: Stock IXChange.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
stx TCP Stock IXChange Ferdi Ladeira -
stx UDP Stock IXChange Ferdi Ladeira -

Registry dates for this port: last modified 2022-01-25.

Check what is listening on port 527

Linux: is anything listening on TCP 527?
sudo ss -tlnp 'sport = :527'
Linux: UDP 527
sudo ss -ulnp 'sport = :527'
Linux / macOS: which process owns the port
sudo lsof -nP -i :527
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':527 '
Windows (Command Prompt)
netstat -ano | findstr :527
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 527 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 527
From Windows
Test-NetConnection HOST -Port 527
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 527

Block port 527 in the firewall

ufw
sudo ufw deny 527/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 527 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 527 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 527' -Direction Inbound -Protocol TCP -LocalPort 527 -Action Block
ufw
sudo ufw deny 527/udp
iptables
sudo iptables -A INPUT -p udp --dport 527 -j DROP
nftables
sudo nft add rule inet filter input udp dport 527 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 527' -Direction Inbound -Protocol UDP -LocalPort 527 -Action Block

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