hydrasketch.js

s = new WebSocket('wss://192.168.0.129/piezo');
var dd=0
s.onmessage=msg=>{
  let d = msg.data.split(",").map(e=>e*1)
  dd = Math.max(...d)/4096
}

d=0
update=()=>d=d*.9+dd*.1
shape().scale(()=>d*10+0.001).out()

piezo_websocket.ino

#include <sstream>

const int analogInPin = A0;  // Analog input pin that the potentiometer is attached to

int sensorValue = 0;        // value read from the pot
int sensorCount = 0;
int sensorPack = 1;

// TODO: Configure your WiFi here
#define WIFI_SSID "aaa"
#define WIFI_PSK  "aaa"

// Max clients to be connected to the chat
#define MAX_CLIENTS 4

// Include certificate data (see note above)
#include "cert.h"
#include "private_key.h"

// We will use wifi
#include <WiFi.h>

// Includes for the server
#include <HTTPSServer.hpp>
#include <SSLCert.hpp>
#include <HTTPRequest.hpp>
#include <HTTPResponse.hpp>
#include <WebsocketHandler.hpp>

// The HTTPS Server comes in a separate namespace. For easier use, include it here.
using namespace httpsserver;

// Create an SSL certificate object from the files included above ...
SSLCert cert = SSLCert(
  example_crt_DER, example_crt_DER_len,
  example_key_DER, example_key_DER_len
);
// ... and create a server based on this certificate.
// The constructor has some optional parameters like the TCP port that should be used
// and the max client count. For simplicity, we use a fixed amount of clients that is bound
// to the max client count.
HTTPSServer secureServer = HTTPSServer(&cert, 443, MAX_CLIENTS);

// Declare some handler functions for the various URLs on the server
// The signature is always the same for those functions. They get two parameters,
// which are pointers to the request data (read request body, headers, ...) and
// to the response data (write response, set status code, ...)
void handleRoot(HTTPRequest * req, HTTPResponse * res);
void handle404(HTTPRequest * req, HTTPResponse * res);

// As websockets are more complex, they need a custom class that is derived from WebsocketHandler
class ChatHandler : public WebsocketHandler {
public:
  // This method is called by the webserver to instantiate a new handler for each
  // client that connects to the websocket endpoint
  static WebsocketHandler* create();

  // This method is called when a message arrives
  void onMessage(WebsocketInputStreambuf * input);

  // Handler function on connection close
  void onClose();
};

// Simple array to store the active clients:
ChatHandler* activeClients[MAX_CLIENTS];

void setup() {
  // Initialize the slots
  for(int i = 0; i < MAX_CLIENTS; i++) activeClients[i] = nullptr;

  // For logging
  Serial.begin(115200);

  // Connect to WiFi
  Serial.println("Setting up WiFi");
  WiFi.begin(WIFI_SSID, WIFI_PSK);
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
    delay(500);
  }
  Serial.print("Connected. IP=");
  Serial.println(WiFi.localIP());

  // For every resource available on the server, we need to create a ResourceNode
  // The ResourceNode links URL and HTTP method to a handler function
  ResourceNode * nodeRoot    = new ResourceNode("/", "GET", &handleRoot);
  ResourceNode * node404     = new ResourceNode("", "GET", &handle404);

  // Add the root node to the server
  secureServer.registerNode(nodeRoot);

  // The websocket handler can be linked to the server by using a WebsocketNode:
  // (Note that the standard defines GET as the only allowed method here,
  // so you do not need to pass it explicitly)
  WebsocketNode * chatNode = new WebsocketNode("/piezo", &ChatHandler::create);

  // Adding the node to the server works in the same way as for all other nodes
  secureServer.registerNode(chatNode);

  // Finally, add the 404 not found node to the server.
  // The path is ignored for the default node.
  secureServer.setDefaultNode(node404);

  Serial.println("Starting server...");
  secureServer.start();
  if (secureServer.isRunning()) {
    Serial.print("Server ready. Open the following URL in multiple browser windows to start chatting: https://");
    Serial.println(WiFi.localIP());
  }
}

std::ostringstream ss;
void loop() {
  // This call will let the server do its work
  secureServer.loop();

  sensorValue = analogRead(analogInPin);
  //Serial.print("sensor = ");
  //Serial.println(sensorValue);

  // Get the input message
  std::string msg;
  ss << sensorValue;
  sensorCount++;
  if (sensorCount >= sensorPack) {
    sensorCount = 0;
    msg = ss.str();
    ss.str("");
    ss.clear();
  
    // Send it back to every client
    for(int i = 0; i < MAX_CLIENTS; i++) {
      if (activeClients[i] != nullptr) {
        activeClients[i]->send(msg, WebsocketHandler::SEND_TYPE_TEXT);
      }
    }
  }
  else {
    ss << ",";
  }

  delay(1);
}

void handle404(HTTPRequest * req, HTTPResponse * res) {
  // Discard request body, if we received any
  // We do this, as this is the default node and may also server POST/PUT requests
  req->discardRequestBody();

  // Set the response status
  res->setStatusCode(404);
  res->setStatusText("Not Found");

  // Set content type of the response
  res->setHeader("Content-Type", "text/html");

  // Write a tiny HTTP page
  res->println("<!DOCTYPE html>");
  res->println("<html>");
  res->println("<head><title>Not Found</title></head>");
  res->println("<body><h1>404 Not Found</h1><p>The requested resource was not found on this server.</p></body>");
  res->println("</html>");
}

// In the create function of the handler, we create a new Handler and keep track
// of it using the activeClients array
WebsocketHandler * ChatHandler::create() {
  Serial.println("Creating new chat client!");
  ChatHandler * handler = new ChatHandler();
  for(int i = 0; i < MAX_CLIENTS; i++) {
    if (activeClients[i] == nullptr) {
      activeClients[i] = handler;
      break;
    }
  }
  return handler;
}

// When the websocket is closing, we remove the client from the array
void ChatHandler::onClose() {
  for(int i = 0; i < MAX_CLIENTS; i++) {
    if (activeClients[i] == this) {
      activeClients[i] = nullptr;
    }
  }
}

// Finally, passing messages around. If we receive something, we send it to all
// other clients
void ChatHandler::onMessage(WebsocketInputStreambuf * inbuf) {
//  // Get the input message
//  std::ostringstream ss;
//  std::string msg;
//  ss << inbuf;
//  msg = ss.str();
//
//  // Send it back to every client
//  for(int i = 0; i < MAX_CLIENTS; i++) {
//    if (activeClients[i] != nullptr) {
//      activeClients[i]->send(msg, SEND_TYPE_TEXT);
//    }
//  }
}



// The following HTML code will present the chat interface.
void handleRoot(HTTPRequest * req, HTTPResponse * res) {
  res->setHeader("Content-Type", "text/html");

  res->print(
    "<!DOCTYPE HTML>\n"
    "<html>\n"
    "   <head>\n"
    "   <title>ESP32 Chat</title>\n"
    "</head>\n"
    "<body>\n"
    "    <div style=\"width:500px;border:1px solid black;margin:20px auto;display:block\">\n"
    "        <form onsubmit=\"return false\">\n"
    "            Your Name: <input type=\"text\" id=\"txtName\" value=\"ESP32 user\">\n"
    "            <button type=\"submit\" id=\"btnConnect\">Connect</button>\n"
    "        </form>\n"
    "        <form onsubmit=\"return false\">\n"
    "            <div style=\"overflow:scroll;height:400px\" id=\"divOut\">Not connected...</div>\n"
    "            Your Message: <input type=\"text\" id=\"txtChat\" disabled>\n"
    "            <button type=\"submit\" id=\"btnSend\" disabled>Send</button>\n"
    "        </form>\n"
    "    </div>\n"
    "    <script type=\"text/javascript\">\n"
    "        const elem = id => document.getElementById(id);\n"
    "        const txtName = elem(\"txtName\");\n"
    "        const txtChat = elem(\"txtChat\");\n"
    "        const btnConnect = elem(\"btnConnect\");\n"
    "        const btnSend = elem(\"btnSend\");\n"
    "        const divOut = elem(\"divOut\");\n"
    "\n"
    "        class Chat {\n"
    "            constructor() {\n"
    "                this.connecting = false;\n"
    "                this.connected = false;\n"
    "                this.name = \"\";\n"
    "                this.ws = null;\n"
    "            }\n"
    "            connect() {\n"
    "                if (this.ws === null) {\n"
    "                    this.connecting = true;\n"
    "                    txtName.disabled = true;\n"
    "                    this.name = txtName.value;\n"
    "                    btnConnect.innerHTML = \"Connecting...\";\n"
    "                    this.ws = new WebSocket(\"wss://\" + document.location.host + \"/chat\");\n"
    "                    this.ws.onopen = e => {\n"
    "                        this.connecting = false;\n"
    "                        this.connected = true;\n"
    "                        divOut.innerHTML = \"<p>Connected.</p>\";\n"
    "                        btnConnect.innerHTML = \"Disconnect\";\n"
    "                        txtChat.disabled=false;\n"
    "                        btnSend.disabled=false;\n"
    "                        this.ws.send(this.name + \" joined!\");\n"
    "                    };\n"
    "                    this.ws.onmessage = e => {\n"
    "                        divOut.innerHTML+=\"<p>\"+e.data+\"</p>\";\n"
    "                        divOut.scrollTo(0,divOut.scrollHeight);\n"
    "                    }\n"
    "                    this.ws.onclose = e => {\n"
    "                        this.disconnect();\n"
    "                    }\n"
    "                }\n"
    "            }\n"
    "            disconnect() {\n"
    "                if (this.ws !== null) {\n"
    "                    this.ws.send(this.name + \" left!\");\n"
    "                    this.ws.close();\n"
    "                    this.ws = null;\n"
    "                }\n"
    "                if (this.connected) {\n"
    "                    this.connected = false;\n"
    "                    txtChat.disabled=true;\n"
    "                    btnSend.disabled=true;\n"
    "                    txtName.disabled = false;\n"
    "                    divOut.innerHTML+=\"<p>Disconnected.</p>\";\n"
    "                    btnConnect.innerHTML = \"Connect\";\n"
    "                }\n"
    "            }\n"
    "            sendMessage(msg) {\n"
    "                if (this.ws !== null) {\n"
    "                    this.ws.send(this.name + \": \" + msg);\n"
    "                }\n"
    "            }\n"
    "        };\n"
    "        let chat = new Chat();\n"
    "        btnConnect.onclick = () => {\n"
    "            if (chat.connected) {\n"
    "                chat.disconnect();\n"
    "            } else if (!chat.connected && !chat.connecting) {\n"
    "                chat.connect();\n"
    "            }\n"
    "        }\n"
    "        btnSend.onclick = () => {\n"
    "            chat.sendMessage(txtChat.value);\n"
    "            txtChat.value=\"\";\n"
    "            txtChat.focus();\n"
    "        }\n"
    "    </script>\n"
    "</body>\n"
    "</html>\n"
  );
}