The CData QuickBooks Desktop Gateway can be used to read and write to QuickBooks POS in situations where direct COM access to QuickBooks POS is not available (e.g., ASP.NET, Java, or QuickBooks POS on a remote machine). Follow the procedure below to connect to QuickBooks POS for the first time through the Desktop Gateway:

1. If you have not already done so, download the CData QuickBooks Desktop Gateway from here and install it.
2. Open the company file you want to connect to in QuickBooks POS using an administrator account in single-user mode.

3. Open the CData QuickBooks Desktop Gateway from the system tray and add a user on the Users tab. Enter a User and Password and select the level of access in the Data Access menu.

   Note: The CData QuickBooks Desktop Gateway does not use the User and Password properties to access QuickBooks POS; the User and Password properties authenticate the user. Authentication to QuickBooks POS is handled by the ApplicationName property.

4. When you first connect, a dialog appears in QuickBooks POS prompting you to authorize the application. After authorizing, you can execute commands to QuickBooks POS. Specify the URL of the Desktop Gateway and the User and Password. By default, the Gateway connects to the currently open company file.
5. If you want to access QuickBooks POS when QuickBooks POS is not running, save the company file information for the user. The Desktop Gateway automatically opens QuickBooks POS in the background with the company file for that user.

NOTE: that if the QuickBooks POS UI is open, you can only connect to that company file. Additionally, the user permissions you specify for the Desktop Gateway must match the user permissions you used for QuickBooks POS. The Desktop Gateway installs as a service in the current user account.

How do I Connect to QuickBooks POS over SSL/TLS?

You can enable SSL/TLS on the Advanced tab.

You will also need to send your public key certificate to the driver. You can do so by setting the SSLServerCert property.