CAN module in STM32F207 - continuously transmitting the same message
CAN modules will retransmit until they see an acknowledgement, so you need at least one other CAN device on the same bus with the same baud rate settings in receive mode. In CAN, the acknowledgement is done inside the ACK bit towards the end of the frame, rather than as a separate message.

More details are in the paper Introduction to the Controller Area Network (CAN) from Texas Instruments. 

It is also important to follow the rules for the terminating resistors, especially at high data rates and/or long cables, but even at lower rates and shorter cables. For example, I have noticed that I can get away with one terminator with a few meters of cable at 125&nbsp;kbaud, and it will not work with no terminators. As the cable gets longer, it becomes necessary to have the two usual terminators. Obviously this is more critical at 1&nbsp;Mbaud.