I am using IIS in my local machine for testing FTP with SSL connection. I am using the FluentFTP library for connecting to the FTP. I am using the following code to connect to the Server.
FtpClient conn = new FtpClient();
conn.Host = firewallSslDetails.Address;
conn.Credentials = new NetworkCredential(firewallSslDetails.UserName, firewallSslDetails.Password);
conn.SslProtocols = System.Security.Authentication.SslProtocols.Default;
X509Certificate2 cert = new X509Certificate2(@"C:\Users\BizTalk360\Desktop\FtpSites\ServerCert.cer");
conn.EncryptionMode = FtpEncryptionMode.Implicit;
conn.DataConnectionType = FtpDataConnectionType.AutoActive;
conn.DataConnectionEncryption = true;
conn.EnableThreadSafeDataConnections = false;
conn.ClientCertificates.Add(cert);
conn.ValidateCertificate += new FtpSslValidation(OnValidateCertificate);
conn.Connect();
The server is returning me with the following error.
FluentFTP.FtpCommandException: Policy requires SSL.; Win32 error: Access is denied.; Error details: SSL policy requires SSL for control channel.;
For connecting over FTP the above code is working fine and for FTP with SSL it is not working.
As you seem to be connecting to the default port 21 (no explicit port specified anywhere), you need to use the "Explicit" mode:
conn.Config.EncryptionMode = FtpEncryptionMode.Explicit;
If the server uses a self-signed certificate, you may need to verify it programmatically. Do not blindly accept any certificate, as the answer by @Ivan does. That's a security flaw. Validate the specific certificate, e.g. by checking its fingerprint.
See FtpWebRequest "The remote certificate is invalid according to the validation procedure".