How can I watch communication in my own network?

Question

I own a Yamaha RX-V479. I can control it with a regular infrared remote and with an app using my smartphone.

I want to develop a small handy interface for my own computer to control the yamaha. Do to so, I need to know, how and which commands my Yamaha accepts. Brute-force is not an option.

So, my current idea is to sniff the network communication between the (iOS) app and the receiver. I expect it is unencrypted while my network (WPA2-PSK) is. My first try running wireshark on my wifi with ip.addr==yamaha did not catch any communication.

My computer is connected with wifi and ethernet, in between is a router, the app works only with wifi and the yamaha is connected via ethernet to the router too. Like that:

How can I monitor the communication?

Answer 1

Introducing an Ethernet HUB or a Switch with Port Mirroring into your network is a simplest way to intercept network traffic between hosts. The device would contact the wireless router, laptop and receiver together.

Diagram

An Ethernet HUB is similar to a Switch but has a distinct difference in operation. A HUB takes incoming traffic and floods it out every port except the port that the traffic originated. While this works great as a simple tap for your purposes, it is too inefficient to be used in modern networks and have been phased out in favor of switches. An over-simplification of switches is that they switch traffic into one port and out a specific port(s). Thus eBay or electronic thrift stores would be the best way to source an Ethernet HUB.

A second option would be to look for a Switch with Port Mirroring or Port Monitoring capabilities. This can be found in some SOHO switches. Some Cisco switches support a proprietary feature called "Switched Port ANalyzer" or SPAN.

A third option would be to intercept the traffic wirelessly. However, I am not knowledgeable enough on the subject to go into great detail. Even so, most would likely agree that the first two options are simpler.

One caveat to note is that the traffic will likely still be protected by higher layer encryption protocol such as SSL or TLS. This is industry best practice. These protocols are commonly used to encrypt HTTP traffic, AKA HTTPS.