"Session operation has timed out" on Azure Function

I'm try to connect to a SFTP server from an Azure Function and I keep getting a "Session operation has timed out". I'm on version "2016.0.0". I've build a similar function using WinSCP and that works fine and the same applies to running the CLI command SFTP from the Kudu prompt.

I'm using the following code:

public static void Run(TimerInfo myTimer, TraceWriter log)
{
string sftp_host = ;
string sftp_user = ;
string sftp_privateKey = @
var stream = new FileStream(sftp_privateKey, FileMode.Open, FileAccess.Read);
var privateKeyFile = new PrivateKeyFile(stream);
AuthenticationMethod authenticationMethod = new PrivateKeyAuthenticationMethod(, privateKeyFile);
ConnectionInfo ConnNfo = new ConnectionInfo(sftp_host, sftp_user, authenticationMethod);
SftpClient client = new SftpClient(ConnNfo);
try
{
client.Connect();

        }
        catch (Exception ex)
            {
                log.Info("Error Message: " + ex.Message);
                client.Disconnect();
            }

}

Start with the SftpClient connection setup shown in the issue, especially client.Connect(), and reproduce the timeout in the Azure Function environment. Compare its behavior with the working WinSCP and Kudu SFTP cases. Done means identifying a reproducible cause or actionable correction for the timeout; the issue does not name a repository file or test to update.