Use SSL with FTP (FTPS)

Using FTPS (FTP protocol over secure SSL channel is easy with Ftp.dll .NET FTPS component. The only difference compared to the FTP protocol is that you need to use ConnectSSL method instead of regular Connect:

// C# version

using (Ftp client = new Ftp())
{
    client.ConnectSSL("ftp.example.org");
    client.Login("username", "password");

    foreach (FtpItem item in client.GetList())
    {
        if (item.IsFolder == true)
            Console.WriteLine("[{0}]", item.Name);
        else
            Console.WriteLine("{0}", item.Name);
    }
    client.Close();
}

' VB.NET version

Using client As New Ftp()

    client.ConnectSSL("ftp.example.org")
    client.Login("username", "password")

    For Each item As FtpItem In client.GetList()
        If item.IsFolder = True Then
            Console.WriteLine("[{0}]", item.Name)
        Else
            Console.WriteLine("{0}", item.Name)
        End If
    Next
    client.Close()
End Using

If your FTP server is using other port than standard 990, you need to use overloaded version of ConnectSSL

// C# version

client.ConnectSSL("ftp.example.org", 999);

' VB.NET version

client.ConnectSSL("ftp.example.org", 999)

The last sample shows how to deal with self-signed certificates:

// C# version

using (Ftp client = new Ftp())
{
    // Use this line to validate self-signed certificates:
    client.ServerCertificateValidate += ValidateCertificate;

    client.ConnectSSL("ftp.example.org");
    client.Login("username", "password");

    foreach (FtpItem item in client.GetList())
    {
        if (item.IsFolder == true)
            Console.WriteLine("[{0}]", item.Name);
        else
            Console.WriteLine("{0}", item.Name);
    }
    client.Close();
}

private static void ValidateCertificate(
    object sender,
    ServerCertificateValidateEventArgs e)
{
    const SslPolicyErrors ignoredErrors =
        SslPolicyErrors.RemoteCertificateChainErrors |
        SslPolicyErrors.RemoteCertificateNameMismatch;

    if ((e.SslPolicyErrors & ~ignoredErrors) == SslPolicyErrors.None)
    {
        e.IsValid = true;
        return;
    }
    e.IsValid = false;
}

' VB.NET version

Using client As New Ftp()
    ' Use this line to validate self-signed certificates:
    AddHandler client.ServerCertificateValidate, AddressOf ValidateCerificate

    client.ConnectSSL("ftp.example.org")
    client.Login("username", "password")

    For Each item As FtpItem In client.GetList()
        If item.IsFolder = True Then
            Console.WriteLine("[{0}]", item.Name)
        Else
            Console.WriteLine("{0}", item.Name)
        End If
    Next
    client.Close()
End Using

Private Sub ValidateCerificate( _
    ByVal sender As Object, _
    ByVal e As ServerCertificateValidateEventArgs)

    Const ignoredErrors As SslPolicyErrors = _
        SslPolicyErrors.RemoteCertificateChainErrors Or _
        SslPolicyErrors.RemoteCertificateNameMismatch

    If (e.SslPolicyErrors And Not ignoredErrors) = SslPolicyErrors.None Then
        e.IsValid = True
        Return
    End If
    e.IsValid = False
End Sub

You can download Ftp.dll FTP/FTPS client for .NET here.

Tags: C# FTP FTP component FTPS VB.NET