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Port 3423 (xtrm)

IANA assigns port 3423 to xtrm: xTrade Reliable Messaging.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
xtrm TCP xTrade Reliable Messaging - -
xtrm UDP xTrade Reliable Messaging - -

Check what is listening on port 3423

Linux: is anything listening on TCP 3423?
sudo ss -tlnp 'sport = :3423'
Linux: UDP 3423
sudo ss -ulnp 'sport = :3423'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3423
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3423 '
Windows (Command Prompt)
netstat -ano | findstr :3423
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3423 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3423
From Windows
Test-NetConnection HOST -Port 3423
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3423

Block port 3423 in the firewall

ufw
sudo ufw deny 3423/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3423 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3423 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3423' -Direction Inbound -Protocol TCP -LocalPort 3423 -Action Block
ufw
sudo ufw deny 3423/udp
iptables
sudo iptables -A INPUT -p udp --dport 3423 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3423 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3423' -Direction Inbound -Protocol UDP -LocalPort 3423 -Action Block

Related ports

3421bmap3422rusb-sys-port3424xtrms3425agps-port

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