Why do the error "LIBSSH2_ERROR_SFTP_PROTOCOL " occurs, while trying to transfer file from the client from another PC?

Question

I am trying to transfer file from one PC(Linux - client) to another PC( where Rebex Tiny Server is running - Windows). The connection is successful, but the code fails to transfer the file. The LIBSSH2_ERROR_SFTP_PROTOCOL error happens while trying to open the file specified as sftp_path (i.e the data folder in rebex).Attaching the code snippet.

 sftp_handle = libssh2_sftp_open(sftp_session, sftppath, 
               LIBSSH2_FXF_WRITE|LIBSSH2_FXF_CREAT|LIBSSH2_FXF_TRUNC,
               LIBSSH2_SFTP_S_IRUSR|LIBSSH2_SFTP_S_IWUSR|
               LIBSSH2_SFTP_S_IRGRP|LIBSSH2_SFTP_S_IROTH);

 if(!sftp_handle &&

           (libssh2_session_last_errno(session) == LIBSSH2_ERROR_SFTP_PROTOCOL)) {
        fprintf(stderr, "Unable to open file with SFTP\n");

        goto shutdown;

}

Answer 1

Make sure your path is correct. If it is, and your code still does not work, please instruct Tiny SFTP Server to log at Debug level and copy&paste the log here.

I just gave this a try and was unable to reproduce the issue. The file was created successfully. I used this C++ code for the client and compiled it on Linux using gcc upload.cpp -lssh2 -o upload command. The app succeeded and created an empty file. My Tiny SFTP Server log looks like this:

15:00:12.103 Debug Server: Accepted connection from 10.0.0.42:52404.
15:00:12.113 Info Server: Session 1: Started on connection from 10.0.0.42:52404.
15:00:12.117 Debug SSH: Session 1: Local SSH version: SSH-2.0-RebexSSH_5.0.8062.0
15:00:12.130 Debug SSH: Session 1: Remote SSH version: SSH-2.0-libssh2_1.10.0
15:00:12.135 Debug SSH: Session 1: Performing algorithm negotiation and key exchange.
15:00:12.207 Debug SSH: Session 1: Performing key exchange using curve25519-sha256 with ssh-rsa.
15:00:12.252 Debug SSH: Session 1: Cipher info: SSH 2.0, curve25519-sha256, ssh-rsa, aes128-ctr/aes128-ctr, hmac-sha2-256/hmac-sha2-256
15:00:12.258 Debug SSH: Session 1: Key exchange finished.
15:00:12.268 Debug SSH: Session 1: Performing authentication.
15:00:12.280 Debug SSH: Session 1: Starting authentication as 'tester' for 'ssh-connection'.
15:00:12.285 Info Server: Session 1: Authentication for 'tester' succeeded.
15:00:12.289 Debug SSH: Session 1: Authenticated as 'tester' for 'ssh-connection'.
15:00:12.298 Debug SSH: Session 1: Received SSH_MSG_CHANNEL_REQUEST: subsystem('sftp').
15:00:12.303 Debug Server: Session 1: Starting acv(1) subsystem.
15:00:12.314 Debug SFTP: Getting item info on '/': success.
15:00:12.338 Debug SFTP: Opening file '/example.txt' (Create, Write): success.
15:00:12.344 Debug SFTP: Closing file '/example.txt': success.
15:00:12.353 Info Server: Session 1: Closed connection from 10.0.0.42:52404.
15:00:12.356 Info SSH: Session 1: Connection close requested.

Comments

Yes you were right!, I was trying with full path "C/Users/xxxx/Downloads/RebexTinySftpServer-Binaries-Latest/data", but it worked with some file name like "\t.txt".

Thank you!

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Yes, that explains it. Tiny SFTP server only exposes the "data" subfolder (by default), and from SFTP client's point of view that's the root directory.