The Capture SDK is not aware of any networking implementations and it requires you to set them in the builder of GiniCapture. The networking related logic is abstracted away behind the GiniCaptureNetworkService interface which is used to upload, analyze and delete documents. You can view the reference documentation for details.
You can provide your own networking by implementing the GiniCaptureNetworkService interface. Just pass your instances to the builder of GiniCapture. Also, you can use Gini Bank API Library for Android or implement the communication with Gini Bank API yourself.