FTP Tutorial

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Table of content

• Namespaces and assemblies
• FTP basics - connecting, logging in and disconnecting
• Working with directories
• Uploading and downloading files
• List of files and directories
• FtpWebRequest - Pluggable Protocol
• Working with proxies
• Using events and logging communication

# Namespaces and assemblies

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

In your source files, import the following namespece:

C#

using Rebex.Net;

VB.NET

Imports Rebex.Net

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# 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.

C#

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();

VB.NET

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.

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# 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.

C#

// 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("..");

VB.NET

'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("..")

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# 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.

C#

// 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");

// upload the 'index.html' file to 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");

VB.NET

'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")

' upload the 'index.html' file to 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")

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# 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:

C#

// 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 
FtpList list = client.GetList ();
foreach (FtpItem item in list)
{
	Console.Write(item.Modified.ToString("u"));
	Console.Write(item.Size.ToString().PadLeft(10,' '));
	Console.Write(" {0}", item.Name);
	Console.WriteLine();
}

VB.NET

'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 FtpList = client.GetList()
Dim item As FtpItem
For Each item In list
    Console.Write(item.Modified.ToString("u"))
    Console.Write(item.Size.ToString().PadLeft(10, ""c))
    Console.Write(" {0}", item.Name)
    Console.WriteLine()
Next item

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# 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.

C#

// register the component for the FTP prefix 
WebRequest.RegisterPrefix("ftp://", 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();

VB.NET

' register the component 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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# Working with proxies

The Ftp class supports connection through proxies of several types. Following proxy types are supported:

C#

// initialize FTP client 
Ftp client = new Ftp();

// setup proxy details  
client.Proxy.ProxyType = FtpProxyType.Socks5;
client.Proxy.Host = proxyHostname;
client.Proxy.Port = proxyPort;

// add proxy username and password when needed 
client.Proxy.UserName = proxyUsername;
client.Proxy.Password = proxyPassword;
			
// connect, login 
client.Connect(hostname, port);			
client.Login(username, password);

// do some work 
// ... 

// disconnect 
client.Disconnect();

VB.NET

' initialize FTP client 
Dim client As Ftp = New Ftp

' setup proxy details  
client.Proxy.ProxyType = FtpProxyType.Socks5
client.Proxy.Host = proxyHostname
client.Proxy.Port = proxyPort

' add proxy username and password when needed 
client.Proxy.UserName = proxyUsername
client.Proxy.Password = proxyPassword

' connect, login 
client.Connect(hostname, port)
client.Login(username, password)

' do some work 
' ... 

' disconnect 
client.Disconnect()

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# Using events and logging communication

In case something goes wrong, it is very useful to have a log of commands sent to the server and responses received from it for diagnostics purposes. To make this possible, the Ftp class declares the following events:

The CommandSent or ResponseRead events are particularly useful for the purpose of generating a communication log and the TransferProgress event can be used by a GUI application to display amount of transfered data or a progress bar.

C#

Ftp client = new Ftp();
client.CommandSent += new FtpCommandSentEventHandler(client_CommandSent);
client.ResponseRead += new FtpResponseReadEventHandler(client_ResponseRead);
client.Connect("ftp.example.org");
...

private void client_CommandSent(object sender, FtpCommandSentEventArgs e)
{
	Console.WriteLine("Command: {0}", e.Command);
}

private void client_ResponseRead(object sender, FtpResponseReadEventArgs e)
{
	Console.WriteLine("Response: {0}", e.Response);
}

VB.NET

Dim client As New Ftp
AddHandler client.CommandSent, AddressOf client_CommandSent
AddHandler client.ResponseRead, AddressOf client_ResponseRead
client.Connect("ftp.example.org")
...

Public Sub client_CommandSent(ByVal sender As Object, ByVal e As _
    FtpCommandSentEventArgs)
	Console.WriteLine("Command: {0}", e.Command)
End Sub 

Public Sub client_ResponseRead(ByVal sender As Object, ByVal e As _
    FtpResponseReadEventArgs)
	Console.WriteLine("Response: {0}", e.Response)
End Sub 

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