If I see it right there could be a segmentation fault if used in echo mode. When you choose echo mode the variable message wouldn't a value assigned and in the cleanup function the not allocated memory would be free'ed.

Option -c enables flowcontrol with rts and cts, for none RS485 mode.
Option -t adds a delay after the reception of the first byte, usable to
test the flowcontrol.

rand was initialized with time(0) which led to the same data if started
twice in the same wall time second.
Now also taking nanoseconds into acount.

BCS 746-000172

The ```gettimeofday()``` function is defined in ```sys/time.h```. Thus
include it.

BCS 746-000125

* Add RS485 echo test for our EMC verification.
* The test is more flexible than the legacy RS485 ping pong test and will
  always recover from transmission errors due to EMI.
* The sent data includes a hard-coded 4-byte header and a 4-byte data length
  field, which is parsed by the receiver. The receiver always scans the
  received data for the header bytes in order to detect a new message.

BCS 746-000125