/// <summary>
/// Starts the asynchronous authentication process.
/// </summary>
/// <param name="callback">The method to call when the authentication is complete.</param>
public void BeginAuthenticate(HandShakeComplete callback)
{
_callBack = callback;
Endpoint.BeginSend(GetAuthenticationBytes(), 0, 3 + Username.Length + Password.Length, SocketFlags.None, OnSent, Endpoint);
}