P5 to Processing

index.js

/* this is your node server, put it somewhere public 
then call 

npm install websockets --save

then node index.js

*/

var WebSocketServer = require('websocket').server;
var http = require('http');
var connections = [];
var server = http.createServer(function(request, response) {
    // process HTTP request. Since we're writing just WebSockets server
    // we don't have to implement anything.
});
server.listen(8081, function() { });

// create the server
wsServer = new WebSocketServer({
    httpServer: server
});

// WebSocket server
wsServer.on('request', function(request) {
    var connection = request.accept(null, request.origin);

    // This is the most important callback for us, we'll handle
    // all messages from users here.
    connection.on('message', function(message) {
            // process WebSocket message
            for( var i = 0; i < connections.length; i++ ){
                if(connections[i] != this ) {
                        connections[i].send(JSON.stringify(message));
                }
            }
    });

    connection.on('close', function(connection) {
        // close user connection
        connections.splice(connections.indexOf(connection), 1);
    });

    connections.push(connection);
});

websocketClient.pde

/*

Use https://github.com/alexandrainst/processing_websockets to create a websocket

*/

import websockets.*;

WebsocketClient wsc;

void setup(){
  size(200,200);
  String ipAddress = "";
  wsc= new WebsocketClient(this, "ws://"+ipAddress+":8081");
}

void draw(){
}

void webSocketEvent(String msg){
 println(msg);
}

void mousePressed(){
  wsc.sendMessage("hi from processing");
}

wsSketch.js

var connection

function setup() {
  
  createCanvas(500, 500);

  // if user is running mozilla then use it's built-in WebSocket
    window.WebSocket = window.WebSocket || window.MozWebSocket;

    connection = new WebSocket("ws://162.242.237.33:8081");

    connection.onopen = function () {
        // connection is opened and ready to use
    };

    connection.onerror = function (error) {
        // an error occurred when sending/receiving data
    };

    connection.onmessage = function (message) {
        // try to decode json (I assume that each message from server is json)
        try {
            var json = JSON.parse(message.data);
            console.log(json['utf8Data']);
        } catch (e) {
            console.log(message.data);
            return;
        }
        // handle incoming message
    };

}

function mousePressed() {
  connection.send("hi from p5");
}

function draw() {
  background(0);
  ellipse(width/2, height/2, size.x, size.y);
}