Using the FXP Protocol

FXP stands for the File eXchange Protocol. It is a method of transferring data that uses FTP to transfer files from one remote server to another server without routing the file data through the client's connection. As such, it is a server-to-server protocol.

While FXP is referred as a distinct protocol, it is, in fact, simply a clever usage of the standard FTP protocol. No special server set up is required.

Some FTP servers disallow FXP file transfers for security reasons. The FTP client has no way to detect this. If an FXP transfer is attempted on a server that does not allow it, an exception will be thrown.

In practice, making an FXP file transfers means that 2 FTP client objects are used. One for each FTP server. A file is selected on the first client, that client is connected to the source server. A destination path is selected on the second client, that client is connected to the destination server. The first client then initiates a FTP file transfer by asking the destination server to connect to the source server and retrieve the selected file.

For a FXP transfer to work, one client needs to have its FxpPassiveTransfer property set to true. The other client's value for the property needs to be set to false. Also, both clients must use the same value for the RepresentationType and TransferMode properties.

Xceed Ftp for .NET only supports making FXP transfers on unencrypted data channels. This means that when connecting to both source and destination FTP servers, the dataProtection parameter must be DataChannelProtection.Clear. It is, however, permitted for the control channel of either source of destination FTP client to be encrypted.

The FXP functionality is available through both the FtpClient and the FileSystem interfaces.

FXP file transfers using the FtpClient interface

FXP transfers are initiated with the static method FtpClient.FxpCopy(). Before the method is called, the context must be properly set up.

Step by step instructions

Because FtpClient.FxpCopy() is static, two independent FtpClient objects are needed. One client for the source file on the source server, another client for the destination file on the destination server.

Connect to each server using the needed credentials for each server.

Make sure the properties on each FtpClient are valid for FXP transfers.

C#
VB.NET

/* For a FXP transfer, only one client can be setup for passive transfer.
   The FxpServer enumeration allows to select either the source or destination client
   as the one that will be setup as passive.
  
   A FxpServer value is supplied to FtpClient.FxpCopy() */
FxpServer passiveServer = FxpServer.Source;

/* For a FXP transfer, both clients must use the same representation type.
 The default values suit us fine here. */
//sourceClient.RepresentationType = RepresentationType.Binary;
//destinationClient.RepresentationType = RepresentationType.Binary;

/* For a FXP transfer, both clients must use the same transfer mode.
 The default values suit us fine here. */
//sourceClient.TransferMode = TransferMode.Stream;
//destinationClient.TransferMode = TransferMode.Stream;

'         For a FXP transfer, only one client can be setup for passive transfer.
'           The FxpServer enumeration allows to select either the source or destination client
'           as the one that will be setup as passive.
'          
'           A FxpServer value is supplied to FtpClient.FxpCopy() 
        Dim passiveServer As FxpServer = FxpServer.Source

'         For a FXP transfer, both clients must use the same representation type.
'         The default values suit us fine here. 
        'sourceClient.RepresentationType = RepresentationType.Binary;
        'destinationClient.RepresentationType = RepresentationType.Binary;

'         For a FXP transfer, both clients must use the same transfer mode.
'         The default values suit us fine here. 
        'sourceClient.TransferMode = TransferMode.Stream;
        'destinationClient.TransferMode = TransferMode.Stream;

Select source and destination files and call FtpClient.FxpCopy().

C#
VB.NET

// Change the current folder on the source server to get to the file we want
sourceClient.ChangeCurrentFolder( "normal1" );

// Copy a file from the source server's current folder to the destination server giving the file a specific name
FtpClient.FxpCopy( sourceClient, "tvDebug.log", destinationClient, "FxpCopy.xml", passiveServer );

' Change the current folder on the source server to get to the file we want
sourceClient.ChangeCurrentFolder("normal1")

' Copy a file from the source server's current folder to the destination server giving the file a specific name
FtpClient.FxpCopy(sourceClient, "tvDebug.log", destinationClient, "FxpCopy.xml", passiveServer)

// Create a FTP client to control our source server
FtpClient sourceClient = new FtpClient();

// Create a FTP client to control our destination server
FtpClient destinationClient = new FtpClient();

try
{
  // Connect to the source server
  sourceClient.Connect( "localhost", 21 );

  /* FXP transfers cannot be performed over encrypted data channels. While it is ok
   to encrypt the control channel, the data channel must remain clear. The DataChannelProtection.Clear
   value ensures that. */
  //sourceClient.Authenticate( AuthenticationMethod.Tls, VerificationFlags.None, null, DataChannelProtection.Clear );
  
  // Login to the source server
  sourceClient.Login( "normal", "normal" );

  // Connect to the destination server
  destinationClient.CertificateReceived += delegate( object sender, CertificateReceivedEventArgs e )
  {
    e.Action = VerificationAction.Accept;
  };

  destinationClient.Connect( "localhost", 10021 );

  /* FXP transfers cannot be performed over encrypted data channels. While it is ok
   to encrypt the control channel, the data channel must remain clear. The DataChannelProtection.Clear
   value ensures that. */
  //destinationClient.Authenticate( AuthenticationMethod.Ssl, VerificationFlags.None, null, DataChannelProtection.Clear );
  
  // Login to the destination server
  destinationClient.Login( "normal", "normal" );

  /* For a FXP transfer, only one client can be setup for passive transfer.
     The FxpServer enumeration allows to select either the source or destination client
     as the one that will be setup as passive.
    
     A FxpServer value is supplied to FtpClient.FxpCopy() */
  FxpServer passiveServer = FxpServer.Source;

  // Change the current folder on the source server to get to the file we want
  sourceClient.ChangeCurrentFolder( "normal1" );

  // Copy a file from the source server's current folder to the destination server giving the file a specific name
  FtpClient.FxpCopy( sourceClient, "tvDebug.log", destinationClient, "FxpCopy.xml", passiveServer );

  // Copy a file from a specific path on the source server to the destination server using the same name
  FtpClient.FxpCopy( sourceClient, "/SftpFolder5/Folder2/ntprint.inf", destinationClient, "ntprint.inf", passiveServer );

  // Copy a file from a specific path on the source server to a specific folder relative to the current folder on the destination server
  FtpClient.FxpCopy( sourceClient, "/SftpFolder5/Folder2/ntprint.inf", destinationClient, "Folder2/ntprint.inf", passiveServer );
}
finally
{
  if( sourceClient.Connected )
    sourceClient.Disconnect();

  if( destinationClient.Connected )
    destinationClient.Disconnect();
}

      ' Create a FTP client to control our source server
      Dim sourceClient As New FtpClient()

      ' Create a FTP client to control our destination server
      Dim destinationClient As New FtpClient()

      Try
        ' Connect to the source server
        sourceClient.Connect("localhost", 21)

'         FXP transfers cannot be performed over encrypted data channels. While it is ok
'         to encrypt the control channel, the data channel must remain clear. The DataChannelProtection.Clear
'         value ensures that. 
        'sourceClient.Authenticate( AuthenticationMethod.Tls, VerificationFlags.None, null, DataChannelProtection.Clear );

        ' Login to the source server
        sourceClient.Login("normal", "normal")

        ' Connect to the destination server
        AddHandler destinationClient.CertificateReceived, AddressOf AnonymousMethod1

        destinationClient.Connect("localhost", 10021)

'         FXP transfers cannot be performed over encrypted data channels. While it is ok
'         to encrypt the control channel, the data channel must remain clear. The DataChannelProtection.Clear
'         value ensures that. 
        'destinationClient.Authenticate( AuthenticationMethod.Ssl, VerificationFlags.None, null, DataChannelProtection.Clear );

        ' Login to the destination server
        destinationClient.Login("normal", "normal")

'         For a FXP transfer, only one client can be setup for passive transfer.
'           The FxpServer enumeration allows to select either the source or destination client
'           as the one that will be setup as passive.
'          
'           A FxpServer value is supplied to FtpClient.FxpCopy() 
        Dim passiveServer As FxpServer = FxpServer.Source

        ' Change the current folder on the source server to get to the file we want
        sourceClient.ChangeCurrentFolder("normal1")

        ' Copy a file from the source server's current folder to the destination server giving the file a specific name
        FtpClient.FxpCopy(sourceClient, "tvDebug.log", destinationClient, "FxpCopy.xml", passiveServer)

        ' Copy a file from a specific path on the source server to the destination server using the same name
        FtpClient.FxpCopy(sourceClient, "/SftpFolder5/Folder2/ntprint.inf", destinationClient, "ntprint.inf", passiveServer)

        ' Copy a file from a specific path on the source server to a specific folder relative to the current folder on the destination server
        FtpClient.FxpCopy(sourceClient, "/SftpFolder5/Folder2/ntprint.inf", destinationClient, "Folder2/ntprint.inf", passiveServer)
      Finally
        If sourceClient.Connected Then
          sourceClient.Disconnect()
        End If

        If destinationClient.Connected Then
          destinationClient.Disconnect()
        End If
      End Try

FXP file transfers using the FileSystem interface

With the FileSystem interface, FXP transfers are initiated automatically when the context of a call to Copy() meets the requirements for a FXP transfer. Because of this, FXP transfers are disabled by default so that behavior from previous versions is preserved and that you retain control over when FXP transfers are made.

If the context of a transfer doesn't meet requirements or FXP transfers are disabled, a standard FTP transfer is performed. No error message or event is triggered by the decision. The process is automatic.

FXP transfer permissions are controlled by values of the FxpTransferPolicy Enumeration in the FtpConnection.FxpTransferPolicy Property. Then the context for the transfer is set up and the transfer is initiated with a normal call to CopyTo().

Step by step instructions

Two independent FtpConnection objects are needed. One connection for the source file on the source server, another connection for the destination file on the destination server.

Make sure FXP is enabled on each FtpConnection and that the properties are valid for FXP transfers.

C#
VB.NET

/* By default, the FXP transfer policy is to not allow any FXP transfers. */

// Enable FXP uploads on the source client
sourceClient.FxpTransferPolicy = FxpTransferPolicy.AcceptOutgoingTransfers;

// Enable FXP downloads on the destination client
destinationClient.FxpTransferPolicy = FxpTransferPolicy.AcceptIncomingTransfers;

/* For a FXP transfer, only one client can have the FxpPassiveTransfer property set to true.
  The default value for the property is true. So we need to set the property to false
  on one of the two clients. */
destinationClient.FxpPassiveTransfer = false;

/* For a FXP transfer, both clients must use the same transfer mode.
 The default values suit us fine here. */
//sourceClient.TransferMode = TransferMode.Stream;
//destinationClient.TransferMode = TransferMode.Stream;

      ' By default, the FXP transfer policy is to not allow any FXP transfers. 

      ' Enable FXP uploads on the source client
      sourceClient.FxpTransferPolicy = FxpTransferPolicy.AcceptOutgoingTransfers

      ' Enable FXP downloads on the destination client
      destinationClient.FxpTransferPolicy = FxpTransferPolicy.AcceptIncomingTransfers

'       For a FXP transfer, only one client can have the FxpPassiveTransfer property set to true.
'        The default value for the property is true. So we need to set the property to false
'        on one of the two clients. 
      destinationClient.FxpPassiveTransfer = False

'       For a FXP transfer, both clients must use the same transfer mode.
'       The default values suit us fine here. 
      'sourceClient.TransferMode = TransferMode.Stream;
      'destinationClient.TransferMode = TransferMode.Stream;

Select source and destination files and call CopyTo().

C#
VB.NET

AbstractFolder sourceFolder;
AbstractFile sourceFile, destinationFile;

// Copy a file from the source server to the destination server giving the file a specific name
sourceFolder = new FtpFolder( sourceClient, "normal1" );
sourceFile = sourceFolder.GetFile( "tvDebug.log" );
destinationFile = new FtpFile( destinationClient, "FxpCopy.xml" );

/* There is no special method to perform FXP transfers. CopyTo() examines the context
  of the transfer. If it involves FTP files at both source and destination on two different
  servers, the FXP transfer policy and other parameters are valid for FXP, it will be
  initiated. If not, a standard file transfer will be made. */

sourceFile.CopyTo( destinationFile, true );

      Dim sourceFolder As AbstractFolder
      Dim sourceFile, destinationFile As AbstractFile

      ' Copy a file from the source server to the destination server giving the file a specific name
      sourceFolder = New FtpFolder(sourceClient, "normal1")
      sourceFile = sourceFolder.GetFile("tvDebug.log")
      destinationFile = New FtpFile(destinationClient, "FxpCopy.xml")

'       There is no special method to perform FXP transfers. CopyTo() examines the context
'        of the transfer. If it involves FTP files at both source and destination on two different
'        servers, the FXP transfer policy and other parameters are valid for FXP, it will be
'        initiated. If not, a standard file transfer will be made. 

      sourceFile.CopyTo(destinationFile, True)

Putting it all together

C#
VB.NET

// Connect to the source server
using( FtpConnection sourceClient = new FtpConnection( "localhost", 21, "normal", "normal" ) )
{
  sourceClient.TraceWriter = new StreamWriter( @"sourceClient.log", false );

  // Connect to the destination server
  using( FtpConnection destinationClient = new FtpConnection( "localhost", 23, "normal", "normal" ) )
  {
    /* For a FXP transfer, only one client can have the FxpPassiveTransfer property set to true.
     The default value for the property is true. So we need to set the property to false
     on one of the two clients. */
    destinationClient.FxpPassiveTransfer = false;

    /* By default, the FXP transfer policy is to not allow any FXP transfers. */

    // Enable FXP uploads on the source client
    sourceClient.FxpTransferPolicy = FxpTransferPolicy.AcceptOutgoingTransfers;

    // Enable FXP downloads on the destination client
    destinationClient.FxpTransferPolicy = FxpTransferPolicy.AcceptIncomingTransfers;

    AbstractFolder sourceFolder, destinationFolder;
    AbstractFile sourceFile, destinationFile;

    // Copy a file from the source server to the destination server giving the file a specific name
    sourceFolder = new FtpFolder( sourceClient, "normal1" );
    sourceFile = sourceFolder.GetFile( "tvDebug.log" );
    destinationFile = new FtpFile( destinationClient, "FxpCopy.xml" );
    
    /* There is no special method to perform FXP transfers. CopyTo() examines the context
     of the transfer. If it involves FTP files at both source and destination on two different
     servers, the FXP transfer policy and other parameters are valid for FXP, it will be
     initiated. If not, a standard file transfer will be made. */
    
    sourceFile.CopyTo( destinationFile, true );

    // Copy a file from a specific path on the source server to the destination server using the same name
    sourceFile = new FtpFile( sourceClient, @"\SftpFolder5\Folder2\ntprint.inf" );
    destinationFolder = new FtpFolder( destinationClient );
    sourceFile.CopyTo( destinationFolder, true );

    // Copy a file from a specific path on the source server to a specific folder relative to the home folder on the destination server
    sourceFile = new FtpFile( sourceClient, @"\SftpFolder5\Folder2\ntprint.inf" );
    destinationFolder = new FtpFolder( destinationClient, "Folder2" );
    sourceFile.CopyTo( destinationFolder, true );
  }
}

      ' Connect to the source server
      Using sourceClient As New FtpConnection("localhost", 21, "normal", "normal")
        sourceClient.TraceWriter = New StreamWriter("sourceClient.log", False)

        ' Connect to the destination server
        Using destinationClient As New FtpConnection("localhost", 23, "normal", "normal")
'           For a FXP transfer, only one client can have the FxpPassiveTransfer property set to true.
'           The default value for the property is true. So we need to set the property to false
'           on one of the two clients. 
          destinationClient.FxpPassiveTransfer = False

          ' By default, the FXP transfer policy is to not allow any FXP transfers. 

          ' Enable FXP uploads on the source client
          sourceClient.FxpTransferPolicy = FxpTransferPolicy.AcceptOutgoingTransfers

          ' Enable FXP downloads on the destination client
          destinationClient.FxpTransferPolicy = FxpTransferPolicy.AcceptIncomingTransfers

          Dim sourceFolder, destinationFolder As AbstractFolder
          Dim sourceFile, destinationFile As AbstractFile

          ' Copy a file from the source server to the destination server giving the file a specific name
          sourceFolder = New FtpFolder(sourceClient, "normal1")
          sourceFile = sourceFolder.GetFile("tvDebug.log")
          destinationFile = New FtpFile(destinationClient, "FxpCopy.xml")

'           There is no special method to perform FXP transfers. CopyTo() examines the context
'           of the transfer. If it involves FTP files at both source and destination on two different
'           servers, the FXP transfer policy and other parameters are valid for FXP, it will be
'           initiated. If not, a standard file transfer will be made. 

          sourceFile.CopyTo(destinationFile, True)

          ' Copy a file from a specific path on the source server to the destination server using the same name
          sourceFile = New FtpFile(sourceClient, "\SftpFolder5\Folder2\ntprint.inf")
          destinationFolder = New FtpFolder(destinationClient)
          sourceFile.CopyTo(destinationFolder, True)

          ' Copy a file from a specific path on the source server to a specific folder relative to the home folder on the destination server
          sourceFile = New FtpFile(sourceClient, "\SftpFolder5\Folder2\ntprint.inf")
          destinationFolder = New FtpFolder(destinationClient, "Folder2")
          sourceFile.CopyTo(destinationFolder, True)
        End Using
      End Using