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Port 2728 (sqdr)

IANA assigns port 2728 to sqdr: SQDR.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
sqdr TCP SQDR Matthew Orzen -
sqdr UDP SQDR Matthew Orzen -

Check what is listening on port 2728

Linux: is anything listening on TCP 2728?
sudo ss -tlnp 'sport = :2728'
Linux: UDP 2728
sudo ss -ulnp 'sport = :2728'
Linux / macOS: which process owns the port
sudo lsof -nP -i :2728
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':2728 '
Windows (Command Prompt)
netstat -ano | findstr :2728
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 2728 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 2728
From Windows
Test-NetConnection HOST -Port 2728
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 2728

Block port 2728 in the firewall

ufw
sudo ufw deny 2728/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 2728 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 2728 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 2728' -Direction Inbound -Protocol TCP -LocalPort 2728 -Action Block
ufw
sudo ufw deny 2728/udp
iptables
sudo iptables -A INPUT -p udp --dport 2728 -j DROP
nftables
sudo nft add rule inet filter input udp dport 2728 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 2728' -Direction Inbound -Protocol UDP -LocalPort 2728 -Action Block

Related ports

2726tams2727mgcp-callagent2729tcim-control2730nec-raidplus

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