Cannot Connect to SFTP – SSH File Transfer (Latest 3CX Self‑Hosted)

[Serge Dornseiffer]

Hello,

I am experiencing an issue configuring Remote Data Storage via SFTP (SSH File Transfer) on the latest self‑hosted 3CX instance.
When testing the connection, 3CX returns:

“Cannot connect to SFTP – SSH File Transfer.”

In addition, SMB and FTP are also failing in the same environment, although SFTP is the primary concern.

Environment​

• 3CX Version: Latest build (please advise if exact build number is required)
• Deployment: Self‑Hosted (Debian-based 3CX ISO)
• Feature: Remote Backup / Recording Storage
• Protocol: SFTP (Port 22)
  
  Troubleshooting Performed

I have verified the following:

• The SFTP server is reachable from the network.
• Port 22 is open and accessible.
• Firewall rules allow outbound traffic from the 3CX server.
• The SFTP server allows inbound connections from the 3CX IP.
• Credentials are confirmed working from another machine.
• The remote directory exists and has correct write permissions.
• The SFTP Server is on Windows Server 2019 but I tried also on an external FTP server, same issue.
  
  
  
  
• However:
  • The Debian distribution used by 3CX does not allow installation of additional SFTP tools, so I cannot perform a manual SFTP login test directly from the 3CX server.
  • The SFTP server logs do not show any incoming connection attempts from 3CX.
  • SMB and FTP connections also fail.

This suggests that 3CX may not actually be initiating the outbound connection.

Questions:

• Is there a known issue in the latest 3CX build affecting remote storage protocols?
• Are there specific SFTP requirements (authentication method, SSH configuration, cipher restrictions, etc.)?
• Are there additional logs beyond the Activity Log that can confirm whether 3CX is attempting the connection?

Since all remote storage methods are failing, I am wondering whether this may be a broader configuration or version-related issue.

Any assistance would be greatly appreciated.

Best regards,

Serge Dornseiffer

Kind regards,

 

[NikosT_3CX]

@Serge Dornseiffer what is the error you receive when you try to setup the FTP on the PBX side ?
Do you get any errors ?
If so, post a screenshot here with the error ( hide sensitive information ).

 

[Serge Dornseiffer]

Thank you for the quick answer:

Cannot connect to SFTP - SSH File Transfer

 

[Serge Dornseiffer]

No errors on the Windows Server SFTP Side. Log is completely empty unless I try from a regular Windows 11 PC via FileZilla where the SFTP works perfectly. In that case the log just says that I connected successfully. But I I try from 3CX Admin console, log remains empty

 

[NikosT_3CX]

@Serge Dornseiffer if you ssh on the machine where the PBX is installed on and you try to ssh / telnet on port 22 to your sFTP what happens ?

 

[Serge Dornseiffer]

When doing telnet port 22 from 3CX Console, he is trying put does not succeed.
When doing the same from my Windows 11 Workstation it does work. From 3CX Console I can ping successfully to the SFTP Server, but not telnet 22.

The 3CX Server is running on Debian 12 on a Windows 2019 HyperV Server where the SFTP is installed. Everything else works, so I do not believe that I have a network issue.On the HyperV Server, I have disabled the Windows Defender Firewall

 

[KyriacosS_3CX]

When doing telnet port 22 from 3CX Console, he is trying put does not succeed

That shows that it is quite definitely a network issue - check the rules/routing on the vm, the vm host, the ssh service, something is blocking the connection.

 

[Serge Dornseiffer]

Traceroute on port 22works. I tried to install nmap for additional testing, but I do not succeed.

 

[KyriacosS_3CX]

Traceroute is not a valid check on its own - telnet to the SSH port shows definitively if that port is open to the specific host from where the telnet is started. If that fails then something in between is blocking the connection - traceroute just confirms a general IP route exists.