Module client

Summary

A module client is a class that represents a client. It handles commands from outside to the ESP3D, and handles commands from ESP3D to outside.

WebDAV, FTP, SSDP and mDNS are not module clients — they are modules that handle in/out data differently.

The main clients are:

• Serial — full duplex, default output client for printer/CNC
• USB Serial — full duplex, optional output for ESP32-S2/S3 only
• Telnet — full duplex
• WebSocket — full duplex
• HTTP — half duplex for everything except ESP3D commands (full duplex for ESP commands)

General description of data flow

The module client fills a buffer char by char until \n or \r is found or the buffer is full. The data comes from outside: serial port, USB port, telnet, websocket.

The catch of the commands is done by a specific library, and the library informs the module client that a command is received. The module client will then dispatch the command to the ESP3D.

To do that, the module client adds context data to the command:

• client type
• authentication level
• origin of the command
• target of the command
• size of the data
• the data itself

This is called a message.

Dispatch cases

There are 3 cases:

1. Non-ESP command, origin ≠ printer/CNC — the message is transferred to the communication module client with the printer/CNC.
2. ESP command, any origin — the message is transferred to the ESP3D. The origin becomes the target to answer the command.
3. Non-ESP command, origin = printer/CNC — the message is dispatched to all clients.

The messages are stored in a FIFO which can be accessed from different threads on the ESP32, or sequentially on the ESP8266.

Note:

Each message is a unique object — it is not possible to send the same message twice. In case of multiple clients, the message will be duplicated.

Messages are dynamically allocated in memory. When dispatch is done or fails, the message must be freed to avoid any memory leak.

Serial

Serial is a full duplex client and the default output client for printer/CNC. It uses the native Serial library of the ESP32 and ESP8266.

Output → ESP3D

The Serial API allows hooking a function to be called when data is received:

Serials[_serialIndex]->onReceive(receiveSerialCb);

When called, the function reads data char by char until \n or \r is found or the buffer is full. The data is packaged as a message and dispatched to the FIFO list by the flush function.

The handle function dispatches the message to the defined target.

ESP3D → Output

When dispatched, the message is packaged and sent to the targeted output client by the dispatch(ESP3DMessage *message) function.

The message data is delivered by writeBytes(const uint8_t *buffer, size_t size), using availableForWrite() to know how much data can be sent.

USB Serial

USB Serial is a full duplex client and an optional output client for ESP32-S2/S3 only. It uses the esp32-usb-serial library.

The library has two initialization functions:

• usb_serial_init() — basic initialization
• usb_serial_create_task() — creates a dedicated task to handle USB events

If no need to handle USB events, just call usb_serial_init() and do not call usb_serial_create_task().

The USB Serial client has a dedicated task that checks if any supported USB Serial device is connected. It tries all drivers one by one until it finds one that matches the supported ones. If a device is found, it hooks a USB event function and an onReceive function to handle data.