I have two options from google research:

1. Chrome serial api as part of an extension followed by message passing to the web page.
2. Web USB protocol that directly talks to serial devices (requires client to enable advanced features in chrome)

To be clear, I want to talk to serial ports on the client's pc. The idea is that they can plug in an IOT device and then quickly use it with my webpage.

(P.S. I understand the security concerns with this. Would really appreciate non-self-righteous technical answers. )