HowTo: Linux Serial Port Sniffer

A serial port sniffer is a tool that allows you to monitor and log the traffic between two serial devices. In Linux, you can use the socat utility as a serial port sniffer. Here are the steps to use socat as a serial port sniffer:

1. Install socat if it’s not already installed:
   sudo apt-get install socat

2. Determine the serial port you want to sniff. You can use the dmesg command to find the name of the serial port device, such as /dev/ttyUSB0 or /dev/ttyS0.
3. Run socat to sniff the serial port traffic. Use the following command to listen to the serial port:
   sudo socat -d -d pty,raw,echo=0 pty,raw,echo=0


   This command creates two virtual serial ports, such as /dev/pts/2 and /dev/pts/3. Any data that is sent between the two virtual ports will be logged to the console.

4. Connect the two virtual serial ports using a serial cable. This will allow you to monitor the data being transmitted between the devices.
   sudo socat -d -d /dev/ttyUSB0,raw,echo=0 /dev/pts/2,raw,echo=0


   This command connects the real serial port (/dev/ttyUSB0) to the virtual serial port (/dev/pts/2). The data being transmitted between the devices will be logged to the console.

5. Disconnect the two virtual serial ports when you are finished monitoring the traffic.
   sudo killall socat


Using socat as a serial port sniffer can be useful for debugging communication issues between serial devices. Keep in mind that this tool should be used for legitimate purposes only and in compliance with local laws and regulations.