1、Appium的架构：C/S模式
Appium的核心是暴漏REST API的WebServer，appium接收来自客户端的连接请求，监听由客户端发起的命令，在移动设备上执行这些命令，这些命令的执行结果通过带有http的响应来呈现。
官网原文：
Client/Server Architecture
Appium is at its heart a webserver that exposes a REST API. It receives connections from a client, listens for commands, executes those commands on a mobile device, and responds with an HTTP response representing the result of the command execution. The fact that we have a client/server architecture opens up a lot of possibilities: we can write our test code in any language that has a http client API, but it is easier to use one of the Appium client libraries. We can put the server on a different machine than our tests are running on. We can write test code and rely on a cloud service like Sauce Labs to receive and interpret the commands.
