HTTPfy

Port 12345 (italk)

IANA assigns port 12345 to italk: Italk Chat System.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
italk TCP Italk Chat System Takayuki Ito -
italk UDP Italk Chat System Takayuki Ito -

Check what is listening on port 12345

Linux: is anything listening on TCP 12345?
sudo ss -tlnp 'sport = :12345'
Linux: UDP 12345
sudo ss -ulnp 'sport = :12345'
Linux / macOS: which process owns the port
sudo lsof -nP -i :12345
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':12345 '
Windows (Command Prompt)
netstat -ano | findstr :12345
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 12345 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 12345
From Windows
Test-NetConnection HOST -Port 12345
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 12345

Block port 12345 in the firewall

ufw
sudo ufw deny 12345/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 12345 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 12345 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 12345' -Direction Inbound -Protocol TCP -LocalPort 12345 -Action Block
ufw
sudo ufw deny 12345/udp
iptables
sudo iptables -A INPUT -p udp --dport 12345 -j DROP
nftables
sudo nft add rule inet filter input udp dport 12345 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 12345' -Direction Inbound -Protocol UDP -LocalPort 12345 -Action Block

Related ports

12321warehouse-sss12322warehouse12546carb-repl-ctrl12753tsaf

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