Serial Line Sniffer is a serial port logging utility. It listens to the specified serial port and logs all data going through this port in both directions.
You can download it from the following link: https://packetstormsecurity.com/files/download/24754/slsnif-0.3.1.tar.gz
Source: https://packetstormsecurity.com/files/24754/slsnif-0.3.1.tar.gz.html