File empty when downloaded using SSH.NET

Question

I am using SSH.NET to download file from the SFTP and here is my code:

string host = ConfigurationManager.AppSettings["SFTPDomain"];
string username = ConfigurationManager.AppSettings["SFTPUser"];
string password = ConfigurationManager.AppSettings["SFTPPass"];
string remoteFileName = ConfigurationManager.AppSettings["SFTPFileName"].ToString();

using (var sftp = new SftpClient(host, username, password))
{
    sftp.Connect();

    using (var file = File.OpenWrite(FilePath))
    {
        sftp.DownloadFile(remoteFileName, file);
    }

    sftp.Disconnect();
}

The problem is that the file which is csv is downloaded but it does not have any data inside. I changed the remoteFile path as well but still the file is downloaded with null data inside. I tried to check if file exists using

if (sftp.Exists(remoteFileName))
{
}

It always return true even if I change the remoteFileName with "pp".

Can anyone help me what I am doing wrong? Or recommend me another other library to download file from SFTP server. I have tried WinSCP but I am getting hostkey error so I tried to pass correct SshHostKeyFingerprint as guided by the server tutorial. Still I get the hostkey error. Is there any simple library i just need to download file from the SFTP?

Regarding WinSCP host key problem: The tutorial you link to is about your account private key, not about server's (host) key. See WinSCP article on Where do I get SSH host key fingerprint for use with scripting or .NET assembly?. Note that SShNet default behavior to accept any host key is not secure. With SshNet, you should handle HostKeyReceived event and verify the host key. Key verification is enforced by WinSCP to upkeep security. — Martin Prikryl
– Martin Prikryl, Commented Oct 7, 2014 at 6:59
Did you try to debug the download (as SshNet is open source)? Do you have server-side logs? What is the server (software) you are connecting to? — Martin Prikryl
– Martin Prikryl, Commented Oct 7, 2014 at 7:05

score 3 · Accepted Answer · 2018-06-13 19:25:43Z

3

I've seen the same issue. Using SSH.NET's ScpClient instead of SftpClient worked for me. It's a drop-in replacement:

using (ScpClient client = new ScpClient(host, username, password))
{
    client.Connect();

    using (Stream localFile = File.Create(localFilePath))
    {
         client.Download(remoteFilePath, localFile);
    }
}

With ScpClient you only get upload/download functionality instead of the many additional features of SFTP, but this may be good enough for your use-case.

edited Jun 13, 2018 at 19:25

answered Jun 13, 2018 at 19:18

user2852699

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Comments

Peter Holloway · Accepted Answer · 2017-12-01 15:47:36Z

1

Try using:

using (Stream file = File.OpenWrite(FilePath))
{
    sftp.DownloadFile(remoteFileName, file);
}

You need to read the stream from the remote server before saving locally.

answered Dec 1, 2017 at 15:47

Peter Holloway

691 silver badge9 bronze badges

1 Comment

Will Over a year ago

Kudos for a solution rather than a circumvention.

Michael Leung · Accepted Answer · 2022-10-03 09:53:38Z

0

This is a very old question but thought I would put an answer here to save some effort for rookies like me who may encounter similar issue and just search up this question:

Essentially after you call the DownloadFile method and write into the stream, you have to reset the stream position back to beginning:

using (var sftp = new SftpClient(host, username, password))
{
    sftp.Connect();

    using (var file = File.OpenWrite(FilePath))
    {
        sftp.DownloadFile(remoteFileName, file);
        file.Position = 0;
    }

answered Oct 3, 2022 at 9:53

Michael Leung

1

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