HTTPfy

Port 21849 (netspeak-cps)

IANA assigns port 21849 to netspeak-cps: NetSpeak Corp. Credit Processing System.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
netspeak-cps TCP NetSpeak Corp. Credit Processing System Toby Hosterman -
netspeak-cps UDP NetSpeak Corp. Credit Processing System Toby Hosterman -

Check what is listening on port 21849

Linux: is anything listening on TCP 21849?
sudo ss -tlnp 'sport = :21849'
Linux: UDP 21849
sudo ss -ulnp 'sport = :21849'
Linux / macOS: which process owns the port
sudo lsof -nP -i :21849
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':21849 '
Windows (Command Prompt)
netstat -ano | findstr :21849
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 21849 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 21849
From Windows
Test-NetConnection HOST -Port 21849
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 21849

Block port 21849 in the firewall

ufw
sudo ufw deny 21849/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 21849 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 21849 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 21849' -Direction Inbound -Protocol TCP -LocalPort 21849 -Action Block
ufw
sudo ufw deny 21849/udp
iptables
sudo iptables -A INPUT -p udp --dport 21849 -j DROP
nftables
sudo nft add rule inet filter input udp dport 21849 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 21849' -Direction Inbound -Protocol UDP -LocalPort 21849 -Action Block

Related ports

21847netspeak-cs21848netspeak-acd22000snapenetio22001optocontrol

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