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// File transfer & sharing

Port 22537: CaldSoft Backup server file transfer

Port 22537 is assigned by IANA to caldsoft-backup (CaldSoft Backup server file transfer).

22537

How caldsoft-backup works

File transfer & sharing
client:225371/32/33/3caldsoft-backup client:225371/32/33/3caldsoft-backup

Files are sent over port 22537 in pieces and reassembled on the other side.

Transport
TCP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
File transfer & sharing
01 Security

Is port 22537 dangerous?

We have no specific security note for port 22537. Its risk depends on the program actually listening on it. General advice for file transfer & sharing services:

  • Prefer encrypted protocols (SFTP, FTPS, SMB 3 with encryption).
  • Disable anonymous access and restrict shares or exports to known hosts.
  • Never publish file sharing protocols to the Internet.
02 Registry

IANA registry entries for port 22537

ServicePortTransportDescriptionReferenceUpdated
caldsoft-backup 22537 TCP CaldSoft Backup server file transfer - 2011-08-12
-22537-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 22537, and is it reachable?

Linux

sudo ss -ltnup 'sport = :22537'      # process listening on 22537
sudo lsof -nP -i :22537

macOS

sudo lsof -nP -i :22537

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 22537 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 22537
netstat -ano | findstr :22537

From another machine

nmap -p 22537 -sV <host>
nc -zv <host> 22537

Block it in the firewall

sudo ufw deny 22537/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 22537" -Direction Inbound -LocalPort 22537 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 22537 used for?

Port 22537 is assigned by IANA to caldsoft-backup (CaldSoft Backup server file transfer).

Is port 22537 TCP or UDP?

Port 22537 is registered for TCP.

Is it safe to open port 22537?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Prefer encrypted protocols (SFTP, FTPS, SMB 3 with encryption).

How do I check if port 22537 is open?

On Linux run "ss -ltnup 'sport = :22537'", on macOS "lsof -nP -i :22537", and on Windows "netstat -ano | findstr :22537" to see the local process. From another machine, "nmap -p 22537 <host>" shows whether it is reachable.

05 Related
:445 SMB tcp · udp · critical risk :21 FTP tcp · udp · sctp · high risk :139 NetBIOS Session tcp · udp · high risk :69 TFTP udp · tcp · high risk :2049 NFS tcp · udp · sctp · high risk :873 rsync tcp · udp · high risk :20 File Transfer [Default Data] tcp · udp · sctp :115 Simple File Transfer Protocol tcp · udp

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