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Port 379 (is99c)

IANA assigns port 379 to is99c: TIA/EIA/IS-99 modem client.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
is99c TCP TIA/EIA/IS-99 modem client - -
is99c UDP TIA/EIA/IS-99 modem client - -

Check what is listening on port 379

Linux: is anything listening on TCP 379?
sudo ss -tlnp 'sport = :379'
Linux: UDP 379
sudo ss -ulnp 'sport = :379'
Linux / macOS: which process owns the port
sudo lsof -nP -i :379
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':379 '
Windows (Command Prompt)
netstat -ano | findstr :379
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 379 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 379
From Windows
Test-NetConnection HOST -Port 379
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 379

Block port 379 in the firewall

ufw
sudo ufw deny 379/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 379 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 379 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 379' -Direction Inbound -Protocol TCP -LocalPort 379 -Action Block
ufw
sudo ufw deny 379/udp
iptables
sudo iptables -A INPUT -p udp --dport 379 -j DROP
nftables
sudo nft add rule inet filter input udp dport 379 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 379' -Direction Inbound -Protocol UDP -LocalPort 379 -Action Block

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377tnETOS378dsETOS380is99s381hp-collector

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