title: method to sniff usb-serial communication on osx
body: <p>On windows, there are several decent alternatives (mostly paid) which allow you to monitor serial port communications.  On OSX there are lots of terminal applications which let you talk to serial devices but I haven't found a mechanism to monitor serial port communication.</p>
  
  <p>The specific use case is:
  I have a USB-Serial device that lives on /dev/tty.usbmodem99999</p>
  
  <p>I have written an integration test that runs multiple commands (successfully).</p>
  
  <p>However on re-running the command the device does not respond.  I've confirmed (as well as I can) that the device is fine.  It works on other platforms as expected.  However on OSX I can only re-run the tests after resetting the device (power cycle).</p>
  
  <p>My theory is that my code is not releasing the device properly but that's hard to confirm when I can't see the communication between my device and my application.</p>
  
  <p>This application: "<a href="http://www.aggsoft.com/serial-port-monitor.htm" rel="noreferrer">http://www.aggsoft.com/serial-port-monitor.htm</a>" has a 'spy' feature that I have been unable to find similiar functionality to on OSX.  I've experimented with 'serial tools' on osx, but it doesn't look like it does spy operations on a single port, in that case it looks like the use case is as a passthrough between two devices rather than monitoring at the port.</p>
  
  <p>Any thoughts greatly appreciated.</p>
  
  <p>serial library being used is:
  <a href="https://github.com/jacobsa/go-serial" rel="noreferrer">https://github.com/jacobsa/go-serial</a></p>