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Port 4042 (ldxp)

IANA assigns port 4042 to ldxp: LDXP.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
ldxp TCP LDXP Craig Calef -
ldxp UDP LDXP Craig Calef -

Check what is listening on port 4042

Linux: is anything listening on TCP 4042?
sudo ss -tlnp 'sport = :4042'
Linux: UDP 4042
sudo ss -ulnp 'sport = :4042'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4042
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':4042 '
Windows (Command Prompt)
netstat -ano | findstr :4042
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4042 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 4042
From Windows
Test-NetConnection HOST -Port 4042
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 4042

Block port 4042 in the firewall

ufw
sudo ufw deny 4042/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 4042 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 4042 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 4042' -Direction Inbound -Protocol TCP -LocalPort 4042 -Action Block
ufw
sudo ufw deny 4042/udp
iptables
sudo iptables -A INPUT -p udp --dport 4042 -j DROP
nftables
sudo nft add rule inet filter input udp dport 4042 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 4042' -Direction Inbound -Protocol UDP -LocalPort 4042 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.