HTTPfy

Port 2451 (netchat)

IANA assigns port 2451 to netchat.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
netchat TCP netchat Julian Mehnle -
netchat UDP netchat Julian Mehnle -

Check what is listening on port 2451

Linux: is anything listening on TCP 2451?
sudo ss -tlnp 'sport = :2451'
Linux: UDP 2451
sudo ss -ulnp 'sport = :2451'
Linux / macOS: which process owns the port
sudo lsof -nP -i :2451
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':2451 '
Windows (Command Prompt)
netstat -ano | findstr :2451
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 2451 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 2451
From Windows
Test-NetConnection HOST -Port 2451
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 2451

Block port 2451 in the firewall

ufw
sudo ufw deny 2451/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 2451 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 2451 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 2451' -Direction Inbound -Protocol TCP -LocalPort 2451 -Action Block
ufw
sudo ufw deny 2451/udp
iptables
sudo iptables -A INPUT -p udp --dport 2451 -j DROP
nftables
sudo nft add rule inet filter input udp dport 2451 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 2451' -Direction Inbound -Protocol UDP -LocalPort 2451 -Action Block

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2449ratl2450netadmin2452snifferclient2453madge-ltd

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