HTTPfy

Port 2543 (reftek)

IANA assigns port 2543 to reftek: REFTEK.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
reftek TCP REFTEK Phil Davidson -
reftek UDP REFTEK Phil Davidson -

Check what is listening on port 2543

Linux: is anything listening on TCP 2543?
sudo ss -tlnp 'sport = :2543'
Linux: UDP 2543
sudo ss -ulnp 'sport = :2543'
Linux / macOS: which process owns the port
sudo lsof -nP -i :2543
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':2543 '
Windows (Command Prompt)
netstat -ano | findstr :2543
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 2543 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 2543
From Windows
Test-NetConnection HOST -Port 2543
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 2543

Block port 2543 in the firewall

ufw
sudo ufw deny 2543/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 2543 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 2543 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 2543' -Direction Inbound -Protocol TCP -LocalPort 2543 -Action Block
ufw
sudo ufw deny 2543/udp
iptables
sudo iptables -A INPUT -p udp --dport 2543 -j DROP
nftables
sudo nft add rule inet filter input udp dport 2543 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 2543' -Direction Inbound -Protocol UDP -LocalPort 2543 -Action Block

Related ports

2541lonworks22542udrawgraph2544novell-zen2545sis-emt

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