internal UserSession Login(EnvironmentAssessment.Collector.ISession Session)
        {
            string      error     = "";
            string      logintime = "";
            UserSession us        = null;

            this.ServiceUrl = "https://" + Session.Server.Name.ToLower() + "/sdk";
            ServiceTimeout  = COptions.VI_Login_Timeout;

            try
            {
                if (this._vimService == null || this._serviceContent == null)
                {
                    this.Connect();
                }
            }
            catch (VimException ex)
            {
                Common.Log.Write("[VimApi] Connecting to '" + this.ServiceUrl + "' failed: " + ex.Message);
                Session.Error = ex.Message;
                return(null);
            }

            SessionManager sessionManager = new SessionManager(this, this.ServiceContent.SessionManager);

            try
            {
                Common.Log.Write("[VimApi] Connecting to '" + this.ServiceUrl + "' using specified credentials [" + Session.Server.UserName + "]");
                us        = sessionManager.Login(Session.Server.UserName, Session.Server.UserPassword, null);
                logintime = us.LoginTime.ToString();
            }
            catch (VimApi.VimException ex)
            {
                error = ex.Message;
            }
            if (logintime.Length > 0)
            {
                Common.Log.Write("[VimApi] Logged into '" + this.ServiceUrl + "' at " + us.LoginTime + " (" + this.Version.ToString().ToLower() + ").");
                return(us);
            }
            else
            {
                Common.Log.Write("[VimApi] Login into '" + this.ServiceUrl + "' failed: " + error); Session.Error = error; return(null);
            }
        }
        internal UserSession LoginSSPI(EnvironmentAssessment.Collector.ISession Session)
        {
            string      error     = "";
            string      logintime = "";
            UserSession us        = null;

            this.ServiceUrl = "https://" + Session.Server.Name + "/sdk";
            ServiceTimeout  = COptions.VI_Login_Timeout;

            try
            {
                if (this._vimService == null || this._serviceContent == null)
                {
                    this.Connect();
                }
            }
            catch (System.Net.WebException ex)
            {
                Common.Log.Write("[VimApi] Connecting to '" + this.ServiceUrl + "' failed: " + ex.Message);
                Session.Error = ex.Message;
                return(null);
            }

            SessionManager sessionManager = new SessionManager(this, this.ServiceContent.SessionManager);

            if (sessionManager != null)
            {
                Boolean flag = true;

                // get server's fqdn for cross-domain authentication
                string FQDN = Session.Server.Name.Substring(Session.Server.Name.IndexOf('.'));
                Common.Sspi.Credentials.CClientCredential clientCred = new Common.Sspi.Credentials.CClientCredential(Sspi.CPackageNames.Negotiate);

                Common.Sspi.Contexts.CClientContext clientContext = null;

                string os = this.ServiceContent.About.OsType;
                if (os.Contains("win"))
                {
                    string serviceprincipal = "host/" + Session.Server.Name + "@" + FQDN;
                    clientContext = new Common.Sspi.Contexts.CClientContext(clientCred, serviceprincipal, Common.Sspi.Contexts.CContextAttrib.Zero);
                    Log.Write("[SSPI] Initialized client context for connection to Windows-based vCenter (" + os + ") using service principal: " + serviceprincipal);
                }
                else
                {
                    string serviceprincipal = "host/" + Session.Server.Name;
                    clientContext = new Common.Sspi.Contexts.CClientContext(clientCred, serviceprincipal, Sspi.Contexts.CContextAttrib.Zero);
                    Log.Write("[SSPI] Initialized client context for connection to Linux-based vCenter (" + os + ") using service principal: " + serviceprincipal);
                }

                byte[] clientToken  = null;
                byte[] serverToken  = null;
                string clientLocale = "en"; //using default locale, should work according to documentation
                bool   retry        = false;

                Common.Sspi.CSecurityStatus clientStatus;

                while (flag)
                {
                    try //sspi authentication
                    {
                        clientStatus = clientContext.Init(serverToken, out clientToken);
                        Common.Log.Write("[VimApi] Connecting to '" + this.ServiceUrl + "' using Windows Session Credentials [" + Environment.UserDomainName + @"\" + Environment.UserName + "] (SSPI Token)");
                        Common.Log.Write("[SSPI] Client token sent <base64Token>" + Convert.ToBase64String(clientToken) + "</base64Token><locale>" + clientLocale + "</locale>", Log.Verbosity.Debug);
                        us   = sessionManager.LoginBySSPI(Convert.ToBase64String(clientToken), clientLocale);
                        flag = false;
                    }
                    catch (VimApi.VimException e)
                    {
                        if (e.MethodFault is SSPIChallenge)
                        {
                            Common.Log.Write("[VimApi] Responding to SSPI challenge from '" + this.ServiceUrl + "' (SSPI challenge response)");
                            serverToken = Convert.FromBase64String(((SSPIChallenge)e.MethodFault).Base64Token);
                            Log.Write("[SSPI] Server token returned <base64Token>" + ((SSPIChallenge)e.MethodFault).Base64Token + "</base64Token>", Log.Verbosity.Debug);
                        }
                        else if (e.MethodFault is InvalidLogin)
                        {
                            //Log.Write("Login with current credentials (SSPI) failed, please enter credentials: " + e.Message);
                            error = "Login with current credentials (SSPI) failed, please enter credentials: " + e.Message; flag = false;
                        }
                        else
                        {
                            try { logintime = us.LoginTime.ToString(); flag = false; }
                            catch (Exception ex) { error = ex.Message; flag = true; }
                        }
                    }
                    catch (Common.Sspi.CSSPIException e)
                    {
                        error = "Login with current credentials (SSPI) unsupported, please enter credentials: " + e.Message; flag = false;
                    }
                    catch (Exception e)
                    {
                        error = "Login with current credentials (SSPI) unsupported, please enter credentials: Server does not have SSPI authentication configured."; flag = false;
                    }
                }
                if (logintime.Length == 0)
                {
                    if (us != null)
                    {
                        if (us.LoginTime != null)
                        {
                            logintime = us.LoginTime.ToString();
                        }
                    }
                }
            }

            if (logintime.Length > 0)
            {
                Common.Log.Write("[VimApi] Logged into '" + this.ServiceUrl + "' at " + us.LoginTime + " (" + this.Version.ToString().ToLower() + ").");
                return(us);
            }
            else
            {
                Common.Log.Write("[VimApi] Login into '" + this.ServiceUrl + "' failed: " + error);
                Session.Error = error;
                return(null);
            }
        }