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Port 103 (gppitnp)

IANA assigns port 103 to gppitnp: Genesis Point-to-Point Trans Net.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
gppitnp TCP Genesis Point-to-Point Trans Net - -
gppitnp UDP Genesis Point-to-Point Trans Net - -

Check what is listening on port 103

Linux: is anything listening on TCP 103?
sudo ss -tlnp 'sport = :103'
Linux: UDP 103
sudo ss -ulnp 'sport = :103'
Linux / macOS: which process owns the port
sudo lsof -nP -i :103
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':103 '
Windows (Command Prompt)
netstat -ano | findstr :103
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 103 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 103
From Windows
Test-NetConnection HOST -Port 103
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 103

Block port 103 in the firewall

ufw
sudo ufw deny 103/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 103 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 103 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 103' -Direction Inbound -Protocol TCP -LocalPort 103 -Action Block
ufw
sudo ufw deny 103/udp
iptables
sudo iptables -A INPUT -p udp --dport 103 -j DROP
nftables
sudo nft add rule inet filter input udp dport 103 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 103' -Direction Inbound -Protocol UDP -LocalPort 103 -Action Block

Related ports

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