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WebSocket Server and Client for Arduino

a WebSocket Server and Client for Arduino based on RFC6455.

Supported features of RFC6455

• text frame
• binary frame
• connection close
• ping
• pong
• continuation frame

Limitations

• max input length is limited to the ram size and the WEBSOCKETS_MAX_DATA_SIZE define
• max output length has no limit (the hardware is the limit)
• Client send big frames with mask 0x00000000 (on AVR all frames)
• continuation frame reassembly need to be handled in the application code

Limitations for Async

• Functions called from within the context of the websocket event might not honor yield() and/or delay(). See this issue for more info and a potential workaround.
• wss / SSL is not possible.

Supported Hardware

• ESP8266 Arduino for ESP8266
• ESP32 Arduino for ESP32
• ESP31B
• Raspberry Pi Pico W Arduino for Pico
• Particle with STM32 ARM Cortex M3
• ATmega328 with Ethernet Shield (ATmega branch)
• ATmega328 with enc28j60 (ATmega branch)
• ATmega2560 with Ethernet Shield (ATmega branch)
• ATmega2560 with enc28j60 (ATmega branch)
• Arduino UNO R4 WiFi
• Arduino Nano 33 IoT, MKR WIFI 1010

Note:

version 2.0.0 and up is not compatible with AVR/ATmega, check ATmega branch.

version 2.3.0 has API changes for the ESP8266 BareSSL (may brakes existing code)

Arduino for AVR not supports std namespace of c++.

wss / SSL

supported for:

• wss client on the ESP8266
• wss / SSL is not natively supported in WebSocketsServer however it is possible to achieve secure websockets by running the device behind an SSL proxy. See Nginx for a sample Nginx server configuration file to enable this.

Root CA Cert Bundles for SSL/TLS connections

Secure connections require the certificate of the server to be verified. One option is to provide a single certificate in the chain of trust. However, for flexibility and robustness, a certificate bundle is recommended. If a server changes the root CA from which it derives its certificates, this will not be a problem. With a single CA cert it will not connect.

• For technical details
• For a PlatformIO setup
• For an example

Including a bundle with all CA certs will use 77.2 kB but this list can be reduced to 16.5 kB for the 41 most common. This results in 90% absolute usage coverage and 99% market share coverage according to W3Techs. The bundle is inserted into the compiled firmware. The bundle is not loaded into RAM, only its index.

ESP Async TCP

This libary can run in Async TCP mode on the ESP.

The mode can be activated in the WebSockets.h (see WEBSOCKETS_NETWORK_TYPE define).

ESPAsyncTCP libary is required.

High Level Client API

• begin : Initiate connection sequence to the websocket host.

void begin(const char *host, uint16_t port, const char * url = "/", const char * protocol = "arduino");
void begin(String host, uint16_t port, String url = "/", String protocol = "arduino");

• onEvent: Callback to handle for websocket events

 void onEvent(WebSocketClientEvent cbEvent);

• WebSocketClientEvent: Handler for websocket events

 void (*WebSocketClientEvent)(WStype_t type, uint8_t * payload, size_t length)

Where WStype_t type is defined as:

  typedef enum {
      WStype_ERROR,
      WStype_DISCONNECTED,
      WStype_CONNECTED,
      WStype_TEXT,
      WStype_BIN,
      WStype_FRAGMENT_TEXT_START,
      WStype_FRAGMENT_BIN_START,
      WStype_FRAGMENT,
      WStype_FRAGMENT_FIN,
      WStype_PING,
      WStype_PONG,
  } WStype_t;

Issues

Submit issues to: https://github.com/Links2004/arduinoWebSockets/issues

License and credits

The library is licensed under LGPLv2.1

libb64 written by Chris Venter. It is distributed under Public Domain see LICENSE.