The local functions of script programmable controller are almost completed, and start to implement the remote-related functions.

The overall architecture of the remote system is as follows:
Use the SDK of ESP8266 to implement tcp server and tcp client.
Write http protocol parsing code on the basis of tcp server, design simple http server, handle data interaction with the browser, including the download of the built-in webpage, and use ajax technology to get the state and save the data.

We use html, js and css to design web pages and download and storage them in the flash of ESP8266 module, in combination with the data processing of c language in the backend, we realise the web-based script programming, status checking, parameter setting and other functions;

On the cloud server side, a linux cloud server host was purchased and swoole was chosen as the TCP/IP communication gateway;

Swoole is a PHP asynchronous network communication engine for production environments, enabling PHP developers to write high-performance asynchronous concurrent TCP, UDP, Unix Socket, HTTP, WebSocket services.

Implement tcp server and websocket server in Swoole framework, in which tcp server is used to connect the controller and the cloud, the controller's tcp client establishes a long TCP connection with the cloud server's tcp server, so that the data from the internet can be sent to the controller remotely via the TCP connection to achieve the remote control of the controller;

The remote web page uses websocket client to establish a long connection with the websocket server of Swoole to achieve remote penetration between the cloud server and the web page, so that the status of the controller can be pushed to the web page in real time for display;

The data between websocket server and tcp server is shared through memory, and the PC tool, web page and controller all have unique numbers, and the data messages between the PC host, controller and web page use this number as the source and destination addresses, and the tcp server and websocket server forward the data messages according to the destination address after receiving them, so as to realise the data transmission on the PC. After receiving the data messages, the tcp server and websocket server will forward them according to the destination address, so as to realise the interconnection of data between the PC tool, web page and controller.

Using redis as the memory database, the status data of the controller can be temporarily stored in the database to realise functions such as abnormal telephone alarms, etc., while mysql is used as the permanent database to store some configuration data.