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Port 5321 (bsfsvr-zn-ssl)

IANA assigns port 5321 to bsfsvr-zn-ssl: Webservices-based Zn interface of BSF over SSL.

Registered (user) port, 1024-49151 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference
bsfsvr-zn-ssl TCP Webservices-based Zn interface of BSF over SSL Bert Paul -

Registry dates for this port: registered 2008-07-03.

Check what is listening on port 5321

Linux: is anything listening on TCP 5321?
sudo ss -tlnp 'sport = :5321'
Linux / macOS: which process owns the port
sudo lsof -nP -i :5321
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':5321 '
Windows (Command Prompt)
netstat -ano | findstr :5321
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 5321 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 5321
From Windows
Test-NetConnection HOST -Port 5321

Block port 5321 in the firewall

ufw
sudo ufw deny 5321/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 5321 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 5321 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 5321' -Direction Inbound -Protocol TCP -LocalPort 5321 -Action Block

Related ports

5319roughtime5320bsfserver-zn5343kfserver5344xkotodrcp

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