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Port 8321 (tnp)

IANA assigns port 8321 to tnp: Thin(ium) Network Protocol.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
tnp TCP Thin(ium) Network Protocol Aly Orady -
tnp UDP Thin(ium) Network Protocol Aly Orady -

Registry dates for this port: registered 2007-08-07.

Check what is listening on port 8321

Linux: is anything listening on TCP 8321?
sudo ss -tlnp 'sport = :8321'
Linux: UDP 8321
sudo ss -ulnp 'sport = :8321'
Linux / macOS: which process owns the port
sudo lsof -nP -i :8321
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':8321 '
Windows (Command Prompt)
netstat -ano | findstr :8321
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 8321 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 8321
From Windows
Test-NetConnection HOST -Port 8321
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 8321

Block port 8321 in the firewall

ufw
sudo ufw deny 8321/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 8321 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 8321 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 8321' -Direction Inbound -Protocol TCP -LocalPort 8321 -Action Block
ufw
sudo ufw deny 8321/udp
iptables
sudo iptables -A INPUT -p udp --dport 8321 -j DROP
nftables
sudo nft add rule inet filter input udp dport 8321 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 8321' -Direction Inbound -Protocol UDP -LocalPort 8321 -Action Block

Related ports

8313hub-open-net8320tnp-discover8322garmin-marine8351server-find

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