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Port 6321 (emp-server1)

IANA assigns port 6321 to emp-server1: Empress Software Connectivity Server 1.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
emp-server1 TCP Empress Software Connectivity Server 1 Srdjan Holovac -
emp-server1 UDP Empress Software Connectivity Server 1 Srdjan Holovac -

Check what is listening on port 6321

Linux: is anything listening on TCP 6321?
sudo ss -tlnp 'sport = :6321'
Linux: UDP 6321
sudo ss -ulnp 'sport = :6321'
Linux / macOS: which process owns the port
sudo lsof -nP -i :6321
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':6321 '
Windows (Command Prompt)
netstat -ano | findstr :6321
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 6321 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 6321
From Windows
Test-NetConnection HOST -Port 6321
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 6321

Block port 6321 in the firewall

ufw
sudo ufw deny 6321/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 6321 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 6321 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 6321' -Direction Inbound -Protocol TCP -LocalPort 6321 -Action Block
ufw
sudo ufw deny 6321/udp
iptables
sudo iptables -A INPUT -p udp --dport 6321 -j DROP
nftables
sudo nft add rule inet filter input udp dport 6321 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 6321' -Direction Inbound -Protocol UDP -LocalPort 6321 -Action Block

Related ports

6318iona-data6320repsvc6322emp-server26324hrd-ncs, hrd-ns-disc

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