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SFTP Connection fails

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Mathias (Author):
It should work if entered correctly. But you need to know what port the target wants.  21 is default for FTP 22 default for SSH.  totally different services..
But since it fails to even connect. something is either wrong with host or port.. Or something is blocking it

moxuanyuan:
I ran into the exact same issue. Here is the reason and how to fix it.

The Root Cause
Multi Commander's built-in SFTP module uses an outdated libssh2 library. It only supports legacy algorithms (like ssh-rsa with SHA-1, diffie-hellman-group14-sha1). Modern Linux servers (Debian 12, Ubuntu 22.04+) disable these by default for security, causing the handshake to fail with (null) errors.

Solution 1: Modify Server Config (Workaround)
If you can manage the server, you can force it to allow legacy algorithms:

Edit SSH config: sudo nano /etc/ssh/sshd_config

Add these lines to the very bottom:

KexAlgorithms +diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha256
Ciphers +aes128-cbc,aes256-cbc,aes128-ctr,aes256-ctr
HostKeyAlgorithms +ssh-rsa
PubkeyAcceptedKeyTypes +ssh-rsa

Restart SSH: sudo systemctl restart ssh

In Multi Commander, clear all keyfile paths and use pure password authentication (it cannot parse modern Ed25519 keys).

Solution 2: Mount as Local Drive (Recommended)
Instead of degrading server security, use tools like RaiDrive or Rclone to mount your SFTP server as a local Windows drive letter (e.g., Z:). You can then manage files in Multi Commander just like a local drive with full speed and modern security.

Hope the developer can update the underlying library soon!

Mathias (Author):
Actually it is libssh2 and Windows issues.. 

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