HTTPfy

Port 21845 (webphone)

IANA assigns port 21845 to webphone.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
webphone TCP webphone Toby Hosterman -
webphone UDP webphone Toby Hosterman -

Check what is listening on port 21845

Linux: is anything listening on TCP 21845?
sudo ss -tlnp 'sport = :21845'
Linux: UDP 21845
sudo ss -ulnp 'sport = :21845'
Linux / macOS: which process owns the port
sudo lsof -nP -i :21845
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':21845 '
Windows (Command Prompt)
netstat -ano | findstr :21845
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 21845 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 21845
From Windows
Test-NetConnection HOST -Port 21845
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 21845

Block port 21845 in the firewall

ufw
sudo ufw deny 21845/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 21845 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 21845 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 21845' -Direction Inbound -Protocol TCP -LocalPort 21845 -Action Block
ufw
sudo ufw deny 21845/udp
iptables
sudo iptables -A INPUT -p udp --dport 21845 -j DROP
nftables
sudo nft add rule inet filter input udp dport 21845 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 21845' -Direction Inbound -Protocol UDP -LocalPort 21845 -Action Block

Related ports

21800tvpm21801sal21846netspeak-is21847netspeak-cs

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