The CertificateReceived event is raised when an FTP server's certificate has been received and verified.
Basic steps
To subscribe to the CertificateReceived event, the following steps must be performed:
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Create an instance of the FtpConnection class.
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Subscribe to the CertificateReceived event.
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If you are using the FtpConnection or FtpClient class in a UI application, assign your form (or any other control that implements the ISynchronizeInvoke interface) to the SynchronizingObject property.
This will insure that events are triggered on the main UI thread, allowing you to perform UI operations in event handlers. It will also make the component automatically call System.Windows.Forms.Application.DoEvents() during blocking operations
The following example demonstrates how the CertificateReceived event can be used. The example also uses the SynchronizingObject property. For a description of how certificates and SSL connections work, see Secure FTP (SSL/TLS).
| VB.NET |
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Imports System
Imports System.Windows.Forms
Imports Xceed.FileSystem
Imports Xceed.Ftp
Private Shared Sub CertificateReceivedExample(ByVal form As Form)
Using connection As New FtpConnection("ftp.myplace.com", 990, "ftp_user_name", "ftp_user_name's remote password", AuthenticationMethod.Tls, VerificationFlags.None, Nothing, DataChannelProtection.Private, True)
' Subscribe to the CertificateReceived event to consult the certificate sent by the server
AddHandler connection.CertificateReceived, AddressOf OnCertificateReceived
' Make events be redirected to the main UI thread and DoEvents() called in the background
connection.SynchronizingObject = form
Dim folder As New FtpFolder(connection)
For Each item As FileSystemItem In folder.GetItems(True)
Console.WriteLine(item.FullName)
Next item
End Using
End Sub
Private Sub OnCertificateReceived(ByVal sender As Object, ByVal e As CertificateReceivedEventArgs)
' Here, we should be in the main UI thread since we set the SynchronizingObject property.
' We can therefore perform UI operations here without worry.
' The Status argument property tells you if the server certificate was accepted
' based on the VerificationFlags you provided.
If e.Status <> VerificationStatus.ValidCertificate Then
Console.WriteLine("The server certificate is invalid: {0}", e.Status.ToString())
Console.WriteLine(e.ServerCertificate.ToString())
' You have three choices here:
'
' 1) Refuse the certificate by setting e.Action to VerificationAction.Reject,
' thus making the authentication fail. This is e.Action's default value
' when the server certificate isn't valid.
'
' 2) Set e.Flags to less restrictive criterion and ask the library to
' validate the certificate again by setting e.Action to
' VerificationAction.VerifyAgain.
'
' 3) Force the library to accept this certificate by setting e.Action to
' VerificationAction.Accept.
'
' We'll do #1 or #3, depending on the user's answer.
Console.WriteLine("Do you want to accept this certificate anyway? [Y/N]")
Dim answer As Integer = Console.Read()
If (answer = AscW("y"c)) OrElse (answer = AscW("Y"c)) Then
e.Action = VerificationAction.Accept
End If
Else
' e.Action's default value is VerificationAction.Accept
Console.WriteLine("Valid certificate received from server.")
End If
End Sub
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| C# |
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using System;
using System.Windows.Forms;
using Xceed.FileSystem;
using Xceed.Ftp;
private static void CertificateReceivedExample( Form form )
{
using( FtpConnection connection = new FtpConnection( "ftp.myplace.com", 990,
"ftp_user_name",
"ftp_user_name's remote password",
AuthenticationMethod.Tls,
VerificationFlags.None,
null,
DataChannelProtection.Private,
true ) )
{
// Subscribe to the CertificateReceived event to consult the certificate sent by the server
connection.CertificateReceived += new CertificateReceivedEventHandler( OnCertificateReceived );
// Make events be redirected to the main UI thread and DoEvents() called in the background
connection.SynchronizingObject = form;
FtpFolder folder = new FtpFolder( connection );
foreach( FileSystemItem item in folder.GetItems( true ) )
{
Console.WriteLine( item.FullName );
}
}
}
private void OnCertificateReceived( object sender, CertificateReceivedEventArgs e )
{
/* Here, we should be in the main UI thread since we set the SynchronizingObject property.
* We can therefore perform UI operations here without worry. */
// The Status argument property tells you if the server certificate was accepted
// based on the VerificationFlags you provided.
if( e.Status != VerificationStatus.ValidCertificate )
{
Console.WriteLine( "The server certificate is invalid: {0}", e.Status.ToString() );
Console.WriteLine( e.ServerCertificate.ToString() );
// You have three choices here:
//
// 1) Refuse the certificate by setting e.Action to VerificationAction.Reject,
// thus making the authentication fail. This is e.Action's default value
// when the server certificate isn't valid.
//
// 2) Set e.Flags to less restrictive criterion and ask the library to
// validate the certificate again by setting e.Action to
// VerificationAction.VerifyAgain.
//
// 3) Force the library to accept this certificate by setting e.Action to
// VerificationAction.Accept.
//
// We'll do #1 or #3, depending on the user's answer.
Console.WriteLine( "Do you want to accept this certificate anyway? [Y/N]" );
int answer = Console.Read();
if( ( answer == 'y' ) || ( answer == 'Y' ) )
{
e.Action = VerificationAction.Accept;
}
}
else
{
// e.Action's default value is VerificationAction.Accept
Console.WriteLine( "Valid certificate received from server." );
}
}
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