(.NET Core C#) SFTP Upload Large File in Parts

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Demonstrates how to split a large file into N parts and then upload each part separately. This technique can be used to potentially avoid limits a SFTP server might impose on upload file size.

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// This example assumes the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

Chilkat.SFtp sftp = new Chilkat.SFtp();

// Set some timeouts, in milliseconds:
sftp.ConnectTimeoutMs = 5000;
sftp.IdleTimeoutMs = 10000;

// Connect to the SSH server.  
// The standard SSH port = 22
// The hostname may be a hostname or IP address.
string hostname = "sftp.example.com";
int port = 22;
bool success = sftp.Connect(hostname,port);
if (success != true) {
    Debug.WriteLine(sftp.LastErrorText);
    return;
}

// Authenticate with the SSH server.  Chilkat SFTP supports
// both password-based authenication as well as public-key
// authentication.  This example uses password authenication.
success = sftp.AuthenticatePw("myLogin","myPassword");
if (success != true) {
    Debug.WriteLine(sftp.LastErrorText);
    return;
}

// After authenticating, the SFTP subsystem must be initialized:
success = sftp.InitializeSftp();
if (success != true) {
    Debug.WriteLine(sftp.LastErrorText);
    return;
}

// Open a remote file for writing on the SSH server.
// If the file already exists, it is overwritten.
// (Specify "createNew" instead of "createTruncate" to
// prevent overwriting existing files.)
string handle = sftp.OpenFile("big.zip","writeOnly","createTruncate");
if (sftp.LastMethodSuccess != true) {
    Debug.WriteLine(sftp.LastErrorText);
    return;
}

// We're going to upload the local file "qa_data/zips/big.zip" (a relative local path from our current working directory)
// to the SFTP server.
string localFilePath = "qa_data/zips/big.zip";

// Rather than uploading in one shot, we'll read the local file in chunks
// and upload a chunk at a time.
Chilkat.FileAccess fac = new Chilkat.FileAccess();

success = fac.OpenForRead(localFilePath);
if (success == false) {
    sftp.CloseHandle(handle);
    Debug.WriteLine(fac.LastErrorText);
    return;
}

// If we were to split the local file into 128K chunks, how many chunks (blocks) would
// we have, including the last partial block?
int blockSize = 131072;
int numBlocks = fac.GetNumBlocks(blockSize);
Debug.WriteLine("Number of blocks = " + Convert.ToString(numBlocks));

Chilkat.BinData bd = new Chilkat.BinData();
int i = 0;
while (i < numBlocks) {
    // Read the Nth block, which gets appended to the bd.  (which means
    // we must clear the contents of bd before the next iteration)
    success = fac.ReadBlockBd(i,blockSize,bd);
    if (success == false) {
        sftp.CloseHandle(handle);
        Debug.WriteLine(fac.LastErrorText);
        return;
    }

    // Upload this block to the open remote file.
    success = sftp.WriteFileBd(handle,bd);
    if (success == false) {
        Debug.WriteLine(sftp.LastErrorText);
        return;
    }

    // Clear the contents for the next iteration.
    bd.Clear();

    i = i + 1;
}

// Close the local file.
fac.FileClose();

// -----------------------------------------------------------------------------
// This is important.  You must close the handle on the server.
// Otherwise open handles will accumulate on the server until eventually a limit
// is reached and the server will fail on a call to OpenFile.
// -----------------------------------------------------------------------------

// Close the remote file handle on the server.
success = sftp.CloseHandle(handle);
if (success != true) {
    Debug.WriteLine(sftp.LastErrorText);
    return;
}

Debug.WriteLine("Success.");