LaunchPad development board talking to itself using a CAN bus
The TM4C123 has two CAN peripherals, but the Launchpad board seems to expose only one of them (CAN0) on its headers.  At first glance that would suggest that you can't do it from one peripheral to another.

Two possible solutions spring to mind:


Most CAN modules support loopback mode, i.e. a module can be configured to receive its own transmission.
If you can access just one of CAN1's pins, either Tx or Rx, then you could use CAN1 to transmit to CAN0, or CAN0 to transmit to CAN1, but not the reverse.


Either solution is probably adequate for testing, and in both cases you wouldn't need to bother with the MCP2551's.