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Logging in and out

Tap the launcher icon to start T.Flex. Type your username and password for the TASSTA network and press the CONNECT button to log in to the TASSTA server.

To make T.Flex log in automatically, specify the User name and Password options and enable the Autologin option in the application settings.

If you want to change your password, use the Reset password item in the navigation drawer.

Connection security details

All TASSTA applications use an encrypted connection that enables authentication, session management, and access control mechanisms. All data between clients and servers is exchanged through encrypted channels. This protects the connection from active eavesdropping and passive disclosure in the network traffic. It also prevents session fixation attacks during the authentication or authorization processes.

In order to manage access to enterprise networks, the TASSTA administrator has the ability to assign rights and permissions to any TASSTA user in T.Commander. Any TASSTA client must be configured with proper connection settings before attempting to log in.

All important connection settings in T.Flex are contained in the Settings menu. For details about configuring them, see Settings.


The T.Flex client application uses the HTTPS protocol for communication with the server. This makes data exchange robust and secure.

Voice encryption

By default, all TASSTA communication traffic is encrypted with TLS using 256-bit AES-SHA. The client and the server authenticate using digital certificates. The standard TASSTA server does not support voice encryption. However, the encryption option can be used on demand. If the specific encryption algorithm is not defined, TASSTA will offer an Authenticated-Encryption Algorithm with blockcipher: AES128, AES192, and AES256 specified in ISO/IEC 19772:2009.

Secure logout

To improve safety, T.Flex provides an additional authentication mechanism on logout. This is controlled through T.Commander and can be enabled by the TASSTA network administrator. The feature forces the user to enter a specific password for logout.

QR code-based authentication

QR code-based authentication can be useful in some operating conditions and has the additional advantage of applying preconfigured T.Flex settings.

  1. Tap the QR code icon on the login screen of the application. You will be prompted to scan a code with your camera in a few moments.
  2. Focus the camera and scan the code. T.Flex logs in, and new settings are applied automatically.

Account switching

The instance of T.Flex installed on your device can store authentication profiles for more than one TASSTA user account. You can set up multiple users and switch from one user to another on the fly without having to log out and log in as a different user.

Selecting the user for login

On the login screen, you may want to change the user that you want to log in as. For that, tap Settings and then tap Accounts in the configuration settings editor. In the list that opens, tap the user you want and then tap the back arrow to return to the login screen.

Switching users mid-session

When you are logged in and multiple user accounts are defined on the device, the Switch account Switch account icon is available in the navigation drawer. Tap the icon to select one of the other accounts stored on the device. In the Switch account popup that opens, tap the item you want and tap OK.

The account switch occurs immediately, and a new connection is established.

Configuring users

To add, edit and delete user account profiles, you need to be logged out. When you are logged in, these tools are not available.

On the login screen, tap Settings and then tap Accounts in the configuration settings editor to open the account list. You can do the following:

  • To add an account to the list, tap Add and specify the following:
    • Display name
      This name is strictly for your convenience to help you easily tell the accounts apart.
    • User name
    • Password
    • Server
    • Port
  • To modify an existing account, tap it in the list and then tap Edit to change the settings listed above.
  • To delete an item from the account list, tap the trash can icon Delete account next to that item. You cannot delete the item that is currently selected; to delete it, first switch to some other item.
  • The User name, Password, Server and Port options outside the account list editor refer to the currently selected account. Modifying them applies the changes only to that account.
  • The accounts you configure don't have to use the same port or even the same server.

Applying connection settings from a configuration file

T.Flex can use connection settings defined in a configuration file. Such files with the .usr extension are created by the administrator in T.Commander, and their contents look like this:


To apply the settings from a .usr file that you obtained from your administrator:

On a device that has a screen:

  1. Make sure the Autologin option is enabled in the applicaton settings.
  2. Put the file in the /Android/data/com.tassta.flex/files/Download directory on the device.
  3. Restart T.Flex. The login with the newly-applied credentials occurs automatically.

On a device without a screen:

  1. Make sure the Autologin and Autostart options are enabled and applied. If either of the settings was previously disabled and you had to enable it, log in to the server again to apply the new permissions.
  2. Put the file in the /Android/data/com.tassta.flex/files/Download directory on the device.
  3. Restart T.Flex. The login with the newly-applied credentials occurs automatically.

If there are multiple .usr files in the downloads directory, T.Flex picks the oldest file. After the settings are applied, all .usr files are deleted from the directory.

Getting the file to the device

If the target device does not have a touchscreen, you have to transfer the file to it over a physical USB connection. To begin, make sure USB debugging is enabled for the device and connect it to the computer you want to copy the file from. Next, do one of the following, whichever method is available or convenient to you:

  • If your OS was able to mount the filesystem of the device, simply use your file manager to copy the file to /Android/data/com.tassta.flex/files/Download on the device.
  • Use the adb utility, and specifically the adb push command, as follows:
    adb push <source_file> <destination_path>
    adb push James.usr /Android/data/com.tassta.flex/files/Download
    (Note that "usr" is not part of the destination path and is followed by whitespace.)

For details about adb, see https://developer.android.com/studio/command-line/adb.