The JSON Wire Protocol is the method by which client and server data are exchanged. It was created by WebDriver's developers. The protocol, according to them, consists of a set of standardised endpoints that are offered to clients VIA a RESTful API. This enables the webdriver to communicate with a server and a client in order to automate tasks. In this protocol, JSON is used to transmit data between the server and the client. Before delivering an object to a server, a client (or the computer running the WebDriver API) turns it into a JSON object. The JSON object is PARSED by the server and converted back to a JavaScript object. The response object is converted to a JSON string by the server and returned to the client. For use, the client transforms the JSON string to a JavaScript object.

In the above IMAGE, we can see the client and the server communicates with each other via JSON wire protocol. The server sends a request to the appium server for running tests and the appium server sends back the response to the main server. 

The mobile JSON Wire Protocol, which is an extension of the Selenium JSON Wire Protocol, is used by Appium. Other than ESTABLISHING up a communication stream, it's used to regulate other mobile phone behaviours.