Port 22537 (caldsoft-backup)

IANA assigns port 22537 to caldsoft-backup: CaldSoft Backup server file transfer.

Registered (user) port, 1024-49151 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference

caldsoft-backup TCP CaldSoft Backup server file transfer CaldSoft -

Registry dates for this port: registered 2011-08-12.

Linux: is anything listening on TCP 22537?

sudo ss -tlnp 'sport = :22537'

Linux / macOS: which process owns the port

sudo lsof -nP -i :22537

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':22537 '

Windows (Command Prompt)

netstat -ano | findstr :22537

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 22537 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 22537

From Windows

Test-NetConnection HOST -Port 22537

ufw

sudo ufw deny 22537/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 22537 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 22537 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 22537' -Direction Inbound -Protocol TCP -LocalPort 22537 -Action Block

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