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Port 4377 (cp-spxsvr)

IANA assigns port 4377 to cp-spxsvr: Cambridge Pixel SPx Server.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
cp-spxsvr TCP Cambridge Pixel SPx Server - -
cp-spxsvr UDP Cambridge Pixel SPx Server - -

Check what is listening on port 4377

Linux: is anything listening on TCP 4377?
sudo ss -tlnp 'sport = :4377'
Linux: UDP 4377
sudo ss -ulnp 'sport = :4377'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4377
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':4377 '
Windows (Command Prompt)
netstat -ano | findstr :4377
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4377 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 4377
From Windows
Test-NetConnection HOST -Port 4377
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 4377

Block port 4377 in the firewall

ufw
sudo ufw deny 4377/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 4377 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 4377 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 4377' -Direction Inbound -Protocol TCP -LocalPort 4377 -Action Block
ufw
sudo ufw deny 4377/udp
iptables
sudo iptables -A INPUT -p udp --dport 4377 -j DROP
nftables
sudo nft add rule inet filter input udp dport 4377 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 4377' -Direction Inbound -Protocol UDP -LocalPort 4377 -Action Block

Related ports

4375tolteces4376bip4378cp-spxdpy4379ctdb

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