μWebSockets

Simple to use implementation of WebSockets for microcontrollers.

List of supported IDEs:

• Arduino
• Visual Studio Code with Platformio
• Microsoft Visual Studio with Visual Micro

List of supported MCUs:

• ATmega328P
• ATmega2560
• Renesas RA4M1 (ARM Cortex-M4)
• SAMD21 (ARM Cortex-M0+)
• STM32 (ARM Cortex-M)
• ESP8266
• ESP32-WROOM-32D

WebSocketServer compatible browsers:

• Chrome
• Edge
• Firefox
• Opera

The Autobahn|Testsuite reports for server and client
^{Some tests will never pass just because of memory lack in ATmega family.}

Table of contents

• μWebSockets
  • Table of contents
  • Requirements
  • Installation
    • config.h
    • Physical connection
  • Usage examples
    • Server
      • Verify clients
      • Subprotocol negotiation
    • Client
    • Chat
  • Approx memory usage
    • Ethernet.h (W5100 and W5500)
    • EthernetENC.h (ENC28j60)
    • WiFi
  • Known issues
  • License

Requirements

• Development board (confirmed working, other boards may or may not work):
  • Arduino Uno (ATmega328P)
  • Arduino Pro Mini (ATmega328P)
  • Arduino Mega2560
  • Arduino Uno R4 Minima/WiFi (ARM Cortex-M4)
  • Arduino Zero / SAMD21 M0 (ARM Cortex-M0)
  • STM Nucleo-64 (ARM Cortex-M)
  • WeMos D1 mini (ESP8266)
  • NodeMCU v3 (ESP8266)
  • ESPDUINO-32 (ESP32-WROOM-32D)
• Ethernet module or shield (confirmed working):
  • Arduino Ethernet Shield (W5100)
  • Arduino Ethernet Shield 2 (W5500)
  • WizNet W5500 module
  • ENC28j60
• Libraries:
  • EthernetENC if you decide to use ENC28j60

Installation

Use Arduino Download Manager or follow this guide.

config.h

Change the following definition if you use a different network controller:

...

#define NETWORK_CONTROLLER ETHERNET_CONTROLLER_W5X00

ETHERNET_CONTROLLER_W5X00
ETHERNET_CONTROLLER_ENC28J60
NETWORK_CONTROLLER_WIFI

ETHERNET_CONTROLLER_W5X00 stands for the official Arduino Ethernet library.

Uncomment these if you want additional information on the serial monitor:

//#define _DEBUG
//#define _DUMP_HANDSHAKE
//#define _DUMP_FRAME_DATA
//#define _DUMP_HEADER

Increase the following value if you expect big data frames (or decrease for devices with a small amount of memory).

constexpr uint16_t kBufferMaxSize{ 256 };

Physical connection

If you have a WeMos D1 in the size of Arduino Uno simply attaching a shield does not work. You have to wire the ICSP on an Ethernet Shield to proper pins.

Ethernet Shield (W5100/W5500)	Arduino Pro Mini	WeMos D1
(ICSP) MISO	PIN 12	D12 / MISO
(ICSP) MOSI	PIN 11	D11 / MOSI
(ICSP) SCK	PIN 13	D13 / SCK
(SS) PIN 10	PIN 10	D10 / SS

W5500 / ENC28j60	Arduino Uno / Pro Mini	Arduino Mega2560
MISO	PIN 12	PIN 50
MOSI	PIN 11	PIN 51
SCS	PIN 10	PIN 53
SCLK	PIN 13	PIN 52

Usage examples

Server

#include <WebSocketServer.h>
using namespace net;

WebSocketServer server{3000};

void setup() {
  // Ethernet/WiFi initialization goes here ...
  // ...

  server.onConnection([](WebSocket &ws) {
    const char message[]{ "Hello from Arduino server!" };
    ws.send(WebSocket::DataType::TEXT, message, strlen(message));

    ws.onClose([](WebSocket &ws, const WebSocket::CloseCode code,
                 const char *reason, uint16_t length) {
      // ...
    });
    ws.onMessage([](WebSocket &ws, const WebSocket::DataType dataType,
                   const char *message, uint16_t length) {
      // ...
    });
  });

  server.begin();
}

void loop() {
  server.listen();
}

Verify clients

// verifyClient callback is called for every header during handshake
// (except for those required by protocol, like "Connection", "Upgrade" etc.)
server.begin([](const IPAddress &ip, const char *header, const char *value) {
  // verify ip ...

  // verify "Origin" header:
  if (strcmp_P(header, (PGM_P)F("Origin")) == 0)
    if (strcmp_P(value, (PGM_P)F("file://")) == 0) return false;

  return true;
});

Subprotocol negotiation

// If you won't pass callback for `protocolHandler` then server will use the
// first requested subprotocol if any
wss.begin(nullptr, [](const char *protocols) {
  // iterate csv protocols and return the one that is supported by your server
  // or nullptr to ignore
});

// You can check client protocol in other callbacks
wss.onConnection([](WebSocket &ws) {
  const auto protocol = ws.getProtocol();
  // ...
  }
});

Node.js server examples here

Client

#include <WebSocketClient.h>
using namespace net;

WebSocketClient client;

void setup() {
  // Ethernet/WiFi initialization goes here ...
  // ...

  client.onOpen([](WebSocket &ws) {
    const char message[]{ "Hello from Arduino client!" };
    ws.send(WebSocket::DataType::TEXT, message, strlen(message));
  });
  client.onClose([](WebSocket &ws, const WebSocket::CloseCode code,
                   const char *reason, uint16_t length) {
    // ...
  });
  client.onMessage([](WebSocket &ws, const WebSocket::DataType dataType,
                     const char *message, uint16_t length) {
    // ...
  });

  client.open("echo.websocket.org", 80);
}

void loop() {
  client.listen();
}

Chat

Node.js server on Raspberry Pi (/node.js/chat.js)

Browser client (/node.js/chat-client.htm)

Arduino Uno client (/examples/chat/chat.ino)

More examples here

Approx memory usage

simple-client.ino example (without debug output, 128 bytes data buffer)

Ethernet.h (W5100 and W5500)

Board	Program space	Dynamic memory
Arduino Uno	24 648 bytes (76%)	829 bytes (40%)
Arduino Mega2560	25 640 bytes (10%)	857 bytes (10%)
Arduino Pro Mini	24 648 bytes (80%)	829 bytes (40%)
Arduino Zero	30 596 bytes (11%)	3 056 bytes (9%)
Arduino Uno R4 Minima	63 860 bytes (24%)	3 620 bytes (11%)

EthernetENC.h (ENC28j60)

Board	Program space	Dynamic memory
Arduino Uno	31 062 bytes (96%)	1 406 bytes (68%)
Arduino Mega2560	32 074 bytes (12%)	1 406 bytes (17%)
Arduino Pro Mini	31 062 bytes (101%)	1 406 bytes (68%)
Arduino Zero	36 796 bytes (14%)	3 684 bytes (11%)

WiFi

Board	Program space	Dynamic memory
Generic ESP8266	286 328 bytes (29%)	27 356 bytes (33%)
WeMos D1 mini	286 328 bytes (27%)	27 356 bytes (33%)
NodeMCU	286 328 bytes (27%)	27 356 bytes (33%)
Arduino Uno R4 WiFi	57 596 bytes (21%)	4 492 bytes (13%)

Known issues

...

License

• This project is licensed under the MIT License - see the LICENSE file for details
• arduino-base64 licensed under licensed under MIT License
• arduinolibs licensed under the MIT
• utf8_check licensed under the MIT