Could not transmit XML to the server

Description of Error:

When attempting to perform some action in ESC that posts to QuickBooks, one of the following errors appears:

Could not transmit xml to server: Object reference not set to an instance of an object.

OR

Could not transmit XML to server: Unable to write data to the transport connection: An established connection was aborted by the software in your host machine.

Cause of Error:

This is caused when ESC knows it should be able to connect to QuickBooks, but is unable to do so for some reason.

Resolution:

To fix this issue perform the following steps:

1. Locate the ESC Accounting Server and verify that it is connected to QuickBooks. Note the Server Name and IP address of the computer that is running the Accounting Server (this can be found in the upper left-hand corner). 
2. Go to the computer that received the error and log on to the desired company in ESC.
3. Go to File → QuickBooks Connection Wizard and click Next.
4. Make sure Connect through the Accounting Server is selected and choose Next.
5. Enter the Server Name or IP address in the Server field and click Next. If the computer running the ESC Accounting Server does not have a static IP address it is a better idea to use the computer name field here.
6. Verify that the connection is successful and click Exit. This should resolve the issue.