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Port 2840 (l3-exprt)

IANA assigns port 2840 to l3-exprt.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
l3-exprt TCP l3-exprt - -
l3-exprt UDP l3-exprt - -

Check what is listening on port 2840

Linux: is anything listening on TCP 2840?
sudo ss -tlnp 'sport = :2840'
Linux: UDP 2840
sudo ss -ulnp 'sport = :2840'
Linux / macOS: which process owns the port
sudo lsof -nP -i :2840
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':2840 '
Windows (Command Prompt)
netstat -ano | findstr :2840
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 2840 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 2840
From Windows
Test-NetConnection HOST -Port 2840
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 2840

Block port 2840 in the firewall

ufw
sudo ufw deny 2840/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 2840 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 2840 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 2840' -Direction Inbound -Protocol TCP -LocalPort 2840 -Action Block
ufw
sudo ufw deny 2840/udp
iptables
sudo iptables -A INPUT -p udp --dport 2840 -j DROP
nftables
sudo nft add rule inet filter input udp dport 2840 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 2840' -Direction Inbound -Protocol UDP -LocalPort 2840 -Action Block

Related ports

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