If an error occurs when running a job from either Nav or LS One, the error can either be a connection error, that no connection to DD can be made, or that connection is OK but some database processing error occurred. Default ports that DD uses are 16860 and 16850 for DD3 communication and 16750 and 16752 for DD2 communication. These ports have to be open in the firewall so Clients and other DD Services can communicate with each other.
How does DD work, what is going on under the hood?
There are two versions of TransAutomClient.dll that come with DD, DD3, and DD2 controls. DD2 is the older control that was included in version 2 of DD and is used in LS Retail NAV 6.4 and older. DD2 reported error code if something was wrong, but these are no longer used in DD3 and the error codes you get do not tell you much, except error 12288 is still DD cannot be found or is not responding. For all other error codes you need to check the DD Debug to see what is going on.
DD3 is built on separate processes running in the background, and if you look at the Task Manager you see these processes.
This is an overview of to which process a request to DD goes and how the data will be routed between processes.
See also