FTP Tutorial

Applies to: Rebex Total Pack, Rebex File Transfer Pack, Rebex FTP/SSL

Namespaces and assemblies 

To use the features of Rebex for .NET described here, you have to reference the Rebex.Ftp.dll, Rebex.Common.dll and Rebex.Networking.dll assemblies in your project. They contains the Ftp and other classes in Rebex.Net namespace.

In your source files, import the following namespace:

using Rebex.Net;

Imports Rebex.Net

FTP basics - connecting, logging in and disconnecting 

Typical FTP session goes like this:

• Connect to the FTP server
• Login - authenticate with user name and password
• Browse directories and transfer files
• Disconnect

There are many FTP servers that allow anonymous access. You have to call the Login method as well for these: just use "anonymous" for username and your e-mail address for password, or try the "guest" password if you don't want to disclose your e-mail - most FTP servers allow this as well. Or pass null (Nothing in Visual Basic) for username and password to achieve the same thing.

And now let's look at some sample code.

using Rebex.Net;
// ...

// create client and connect
Ftp client = new Ftp();
client.Connect("ftp.example.org");

// authenticate
client.Login("username", "password");

// browse directories, transfer files
// ...

// disconnect
client.Disconnect();

Imports Rebex.Net
' ...

' create client and connect
Dim client As New Ftp
client.Connect("ftp.example.org")

' authenticate
client.Login("username", "password")

' browse directories, transfer files
' ...

' disconnect
client.Disconnect()

During a single FTP session, only one operation such as file transfer can be active at the same time. However, if you really need to transfer more files simultaneously, or browse directories while a file transfer is in progress, you might initiate multiple FTP sessions to the same servers - most servers are configured to allow this.

Working with directories 

Working with directories (folders) on the FTP server is simple. The remote filesystem is organized in the same way as in Un*x. If you are used to Windows, watch out for the two differencies - a slash (/) is used instead of a backslash, and there is only a single root at "/", no drive letters. A typical path to a file might look like "/pub/incoming/test.zip", for example.

// create client, connect and log in
Ftp client = new Ftp();
client.Connect("ftp.example.org");
client.Login("username", "password");

// determine current directory
Console.WriteLine("Current directory: {0}", client.GetCurrentDirectory());

// create the 'top' directory at the root level
client.CreateDirectory("/top");

// create the 'first' directory in the '/top' directory
client.CreateDirectory("/top/first");

// change the current directory to '/top'
client.ChangeDirectory("/top");

// create the 'second' directory in the current folder
// (note: we used a relative path this time)
client.CreateDirectory("second");

// remove the 'first' directory we created earlier
client.RemoveDirectory("first");

// change the current directory to a parent,
// (note: '..' has the same meaning as in Windows and Un*x
client.ChangeDirectory("..");

' create client, connect and log in
Dim client As New Ftp
client.Connect("ftp.example.org")
client.Login("username", "password")

' determine current directory
Console.WriteLine("Current directory: {0}", client.GetCurrentDirectory())

' create the 'top' directory at the root level
client.CreateDirectory("/top")

' create the 'first' directory in the '/top' directory
client.CreateDirectory("/top/first")

' change the current directory to '/top'
client.ChangeDirectory("/top")

' create the 'second' directory in the current folder
' (note: we used a relative path this time)
client.CreateDirectory("second")

' remove the 'first' directory we created earlier
client.RemoveDirectory("first")

' change the current directory to a parent,
' (note: '..' has the same meaning as in Windows and Un*x
client.ChangeDirectory("..")

Uploading and downloading files 

File transfers are the essential part of the FTP protocol and can be achieved using the GetFile and PutFile methods. They accept the path to the local file and the path to the remote file (both paths must include the filename) and return the number of bytes transferred (as long integer).

Other variants are also available that accept local and remote offsets, or streams instead of local files - it is easy to use .NET's MemoryStream to upload and download data from and to memory instead of disk.

// create client, connect and log in
Ftp client = new Ftp();
client.Connect("ftp.example.org");
client.Login("username", "password");

// upload the 'test.zip' file to the current directory at the server
client.PutFile(@"c:\data\test.zip", "test.zip");

// upload the 'index.html' file to the specified directory at the server
client.PutFile(@"c:\data\index.html", "/wwwroot/index.html");

// download the 'test.zip' file from the current directory at the server
client.GetFile("test.zip", @"c:\data\test.zip");

// download the 'index.html' file from the specified directory at the server
client.GetFile("/wwwroot/index.html", @"c:\data\index.html");

// upload a text using a MemoryStream
string message = "Hello from Rebex FTP for .NET!";
byte[] data = System.Text.Encoding.Default.GetBytes(message);
System.IO.MemoryStream ms = new System.IO.MemoryStream(data);
client.PutFile(ms, "message.txt");

' create client, connect and log in
Dim client As New Ftp
client.Connect("ftp.example.org")
client.Login("username", "password")

' upload the 'test.zip' file to the current directory at the server
client.PutFile("c:\data\test.zip", "test.zip")

' upload the 'index.html' file to the specified directory at the server
client.PutFile("c:\data\index.html", "/wwwroot/index.html")

' download the 'test.zip' file from the current directory at the server
client.GetFile("test.zip", "c:\data\test.zip")

' download the 'index.html' file from the specified directory at the server
client.GetFile("/wwwroot/index.html", "c:\data\index.html")

' upload a text using a MemoryStream
Dim message As String = "Hello from Rebex FTP for .NET!"
Dim data As Byte() = System.Text.Encoding.Default.GetBytes(message)
Dim ms As New System.IO.MemoryStream(data)
client.PutFile(ms, "message.txt")

List of files and directories 

The format of the list of the contents of a directory is not defined by the FTP RFC, and varies substantially from server to server. But with Rebex FTP, retrieving and accessing the list of files in a directory is extremely easy - the GetList method does all the hard work and parses all common list formats automatically!

The following code snippet displays the list of files in the remote directory to a console:

// create client, connect and log in
Ftp client = new Ftp();
client.Connect("ftp.example.org");
client.Login("username", "password");

// select the desired directory
client.ChangeDirectory("path");

// retrieve and display the list of files and directories
FtpItemCollection list = client.GetList();
foreach (FtpItem item in list)
{
    Console.Write(item.LastWriteTime.GetValueOrDefault().ToString("u"));
    Console.Write(item.Length.ToString().PadLeft(10, ' '));
    Console.Write(" {0}", item.Name);
    Console.WriteLine();
}

' create client, connect and log in
Dim client As New Ftp
client.Connect("ftp.example.org")
client.Login("username", "password")

' select the desired directory
client.ChangeDirectory("path")

' retrieve and display the list of files and directories
Dim list As FtpItemCollection = client.GetList()
Dim item As FtpItem
For Each item In list
    Console.Write(item.LastWriteTime.GetValueOrDefault().ToString("u"))
    Console.Write(item.Length.ToString().PadLeft(10, " "c))
    Console.Write(" {0}", item.Name)
    Console.WriteLine()
Next item

Transferring multiple files and directories 

Upload or download of multiple files is a very common task. There are Download and Upload methods that can be used to transfer multiple files easily - just provide the source path (which can be a directory or contain wildcards), destination path and traversal mode.

// create client, connect and log in
Ftp client = new Ftp();
client.Connect("ftp.example.org");
client.Login("username", "password");

// upload the content of 'c:\data' directory and all subdirectories
// to the '/wwwroot' directory at the server
client.Upload(@"c:\data\*", "/wwwroot", TraversalMode.Recursive);

// upload all '.html' files in 'c:\data' directory
// to the '/wwwroot' directory at the server
client.Upload(@"c:\data\*.html", "/wwwroot", TraversalMode.MatchFilesShallow,
    TransferMethod.Copy, ActionOnExistingFiles.OverwriteAll);

// download the content of '/wwwroot' directory and all subdirectories
// at the server to the 'c:\data' directory
client.Download("/wwwroot/*", @"c:\data", TraversalMode.Recursive);

// download all '.html' files in '/wwwroot' directory at the server
// to the 'c:\data' directory
client.Download("/wwwroot/*.html", @"c:\data", TraversalMode.MatchFilesShallow,
    TransferMethod.Copy, ActionOnExistingFiles.OverwriteAll);

' create client, connect and log in
Dim client As New Ftp
client.Connect("ftp.example.org")
client.Login("username", "password")

' upload the content of 'c:\data' directory and all subdirectories
' to the '/wwwroot' directory at the server
client.Upload("c:\data\*", "/wwwroot", TraversalMode.Recursive)

' upload all '.html' files in 'c:\data' directory
' to the '/wwwroot' directory at the server
client.Upload("c:\data\*.html", "/wwwroot", TraversalMode.MatchFilesShallow, _
   TransferMethod.Copy, ActionOnExistingFiles.OverwriteAll)

' download the content of '/wwwroot' directory and all subdirectories
' at the server to the 'c:\data' directory
client.Download("/wwwroot/*", "c:\data", TraversalMode.Recursive)

' download all '.html' files in '/wwwroot' directory at the server
' to the 'c:\data' directory
client.Download("/wwwroot/*.html", "c:\data", TraversalMode.MatchFilesShallow, _
   TransferMethod.Copy, ActionOnExistingFiles.OverwriteAll)

For transferring files from the current directory use asterisk (*). For example client.Download("*", localPath).

When transferring lots of files, things can occasionally go wrong due to unforeseen problems - to be informed about such errors, use ProblemDetected event that also makes it possible to select the desired next action. To stay informed about what is currently going on, use the TransferProgressChanged event.

// add event handler that gets called when a problem is detected during the multi file
// transfer (this is optional) - the event handler can select the desired next action
client.ProblemDetected += new EventHandler<FtpProblemDetectedEventArgs>(client_ProblemDetected);

// add event handler that gets called when significant action occurs during
// traversing hierarchy structure (this is optional)
client.Traversing += new EventHandler<FtpTraversingEventArgs>(client_Traversing);

// add event handler that gets called when a significant action occurs during
// the batch transfer (this is optional)
client.TransferProgressChanged += new EventHandler<FtpTransferProgressChangedEventArgs>(client_TransferProgressChanged);

// upload or download files
client.Upload(localPath, remotePath, TraversalMode.Recursive);

// of course, the client_ProblemDetected, client_Traversing and client_TransferProgressChanged methods
// have to be implemented - check out the FtpBatchTransfer sample for more information

' add event handler that gets called when a problem is detected during the multi file
' transfer (this is optional) - the event handler can select the desired next action
AddHandler client.ProblemDetected, AddressOf client_ProblemDetected

' add event handler that gets called when significant action occurs during
' traversing hierarchy structure (this is optional)
AddHandler client.Traversing, AddressOf client_Traversing

' add event handler that gets called when a significant action occurs during
' the batch transfer (this is optional)
AddHandler client.TransferProgressChanged, AddressOf client_TransferProgressChanged

' upload or download files
client.Upload(localPath, remotePath, TraversalMode.Recursive)

' of course, the client_ProblemDetected, client_Traversing and client_TransferProgressChanged methods
' have to be implemented - check out the FtpBatchTransfer sample for more information

For more information about these events, check out the FTP Batch Transfer sample application!

Transfer compression - MODE Z 

The basic FTP protocol transfers your data as-is without any kind of compression. For highly-compressible data such as text files or database scripts, this is highly inefficient. To solve this, many FTP servers introduced MODE Z, an alternative to MODE S and MODE B. In MODE Z, all transfers are compressed using the ZLIB compression method, making transfers of highly compressible files (such as TXT, BMP or DOC) much faster - this includes FTP directory listings retrieved using GetList, GetRawList or GetNameList methods. On the other hand, MODE Z doesn't provide any substantial speedup for files that are already compresses (such as ZIP, JPEG, PNG or DOCX files).

To enable MODE Z in Rebex FTP, just set the TransferMode property to FtpTransferMode.Zlib. All data transfers will now use MODE Z if the FTP server supports it and fall back to MODE S if it doesn't.

// create client, connect and log in
Ftp client = new Ftp();
client.Connect("ftp.example.org");
client.Login("username", "password");


// change the preferred transfer mode to MODE Z
client.TransferMode = FtpTransferMode.Zlib;

// upload the 'hugelist.txt' file to the specified directory at the server
client.PutFile(@"c:\data\hugelist.txt", "/wwwroot/hugelist.txt");

// download the 'hugelist.txt' file from the specified directory at the server
client.GetFile("/wwwroot/hugelist.txt", @"c:\data\hugelist.txt");


// change the preferred transfer mode to stream mode (default)
client.TransferMode = FtpTransferMode.Stream;

// upload the 'archive.zip' file to the specified directory at the server
client.PutFile(@"c:\data\archive.zip", "/wwwroot/archive.zip");

// download the 'archive.zip' file from the specified directory at the server
client.GetFile("/wwwroot/archive.zip", @"c:\data\archive.zip");

' create client, connect and log in
Dim client As New Ftp
client.Connect("ftp.example.org")
client.Login("username", "password")


' change the preferred transfer mode to MODE Z
client.TransferMode = FtpTransferMode.Zlib

' upload the 'hugelist.txt' file to the specified directory at the server
client.PutFile("c:\data\hugelist.txt", "/wwwroot/hugelist.txt")

' download the 'hugelist.txt' file from the specified directory at the server
client.GetFile("/wwwroot/hugelist.txt", "c:\data\hugelist.txt")


' change the preferred transfer mode to stream mode (default)
client.TransferMode = FtpTransferMode.Stream

' upload the 'archive.zip' file to the specified directory at the server
client.PutFile("c:\data\archive.zip", "/wwwroot/archive.zip")

' download the 'archive.zip' file from the specified directory at the server
client.GetFile("/wwwroot/archive.zip", "c:\data\archive.zip")

FtpWebRequest - Pluggable Protocol 

There is also an alternative way to using the Ftp class to upload and download files using the FTP protocol - the .NET Framework introduced Uri, WebRequest and WebResponse classes for accessing internet resources through a request/response model and includes support for HTTP protocol and file:// scheme to request local files.

Rebex FTP for .NET fits nicely into this model with its FtpWebRequest class, which provides an FTP-specific implementation of WebRequest class. Once registered, WebRequest.Create can be used for accessing files on FTP servers in addition to natively supported HTTP and HTTPS.

// register the library for the FTP prefix
WebRequest.RegisterPrefix("ftp://", Rebex.Net.FtpWebRequest.Creator);

// WebRequest now supports ftp protocol in addition to HTTP/HTTPS
// and local files - the rest of this code snippet is protocol-agnostic

// create web request for the given URI
WebRequest request = WebRequest.Create("ftp://ftp.example.org/files/package.zip");

// get and read web response
WebResponse response = request.GetResponse();
Stream stream = response.GetResponseStream();

Stream local = File.Create("package.zip");

byte[] buffer = new byte[1024];
int n;
do
{
    n = stream.Read(buffer, 0, buffer.Length);
    local.Write(buffer, 0, n);
} while (n > 0);

// close both streams
stream.Close();
local.Close();

' register the library for the FTP prefix
WebRequest.RegisterPrefix("ftp://", Rebex.Net.FtpWebRequest.Creator)

' WebRequest now supports ftp protocol in addition to HTTP/HTTPS
' and local files - the rest of this code snippet is protocol-agnostic

' create web request for the given URI
Dim request As WebRequest = WebRequest.Create("ftp://ftp.example.org/files/package.zip")

' get and read web response
Dim response As WebResponse = request.GetResponse()
Dim stream As Stream = response.GetResponseStream()

Dim local As Stream = File.Create("package.zip")

Dim buffer(1023) As Byte
Dim n As Integer
Do
    n = stream.Read(buffer, 0, buffer.Length)
    local.Write(buffer, 0, n)
Loop While n > 0

' close both streams
stream.Close()
local.Close()

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