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Port 1251 (servergraph)

IANA assigns port 1251 to servergraph.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
servergraph TCP servergraph Lindsay Morris -
servergraph UDP servergraph Lindsay Morris -

Check what is listening on port 1251

Linux: is anything listening on TCP 1251?
sudo ss -tlnp 'sport = :1251'
Linux: UDP 1251
sudo ss -ulnp 'sport = :1251'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1251
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':1251 '
Windows (Command Prompt)
netstat -ano | findstr :1251
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1251 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 1251
From Windows
Test-NetConnection HOST -Port 1251
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1251

Block port 1251 in the firewall

ufw
sudo ufw deny 1251/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 1251 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 1251 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 1251' -Direction Inbound -Protocol TCP -LocalPort 1251 -Action Block
ufw
sudo ufw deny 1251/udp
iptables
sudo iptables -A INPUT -p udp --dport 1251 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1251 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1251' -Direction Inbound -Protocol UDP -LocalPort 1251 -Action Block

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