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Port 377 (tnETOS)

IANA assigns port 377 to tnETOS: NEC Corporation.

Well-known (system) port, 0-1023 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
tnETOS TCP NEC Corporation - -
tnETOS UDP NEC Corporation - -

Check what is listening on port 377

Linux: is anything listening on TCP 377?
sudo ss -tlnp 'sport = :377'
Linux: UDP 377
sudo ss -ulnp 'sport = :377'
Linux / macOS: which process owns the port
sudo lsof -nP -i :377
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':377 '
Windows (Command Prompt)
netstat -ano | findstr :377
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 377 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 377
From Windows
Test-NetConnection HOST -Port 377
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 377

Block port 377 in the firewall

ufw
sudo ufw deny 377/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 377 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 377 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 377' -Direction Inbound -Protocol TCP -LocalPort 377 -Action Block
ufw
sudo ufw deny 377/udp
iptables
sudo iptables -A INPUT -p udp --dport 377 -j DROP
nftables
sudo nft add rule inet filter input udp dport 377 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 377' -Direction Inbound -Protocol UDP -LocalPort 377 -Action Block

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