Service multiple connection on NodeJS webserver - node.js

Question

I have a web server running using Node.js with express and socket.io It displays real-time temperature information and allows for real-time control of some basic hardware controllers.
Each time I connect to the server from a different client, a new instance of the content is delivered as opposed to delivering the last configured instance or state.
Things work fine when just one client is used, but I need to be able to monitor the temperatures and control status from multiple clients.
How can I make sure that no matter which client accesses the server, they all see the same state of the server?
Server code below:
var app = require('express')();
var http = require('http').createServer(app);
var socketServer = require('socket.io').listen(http);
var fs = require('fs');
var csv_stream = fs.createWriteStream("tempLog.csv");
var time_handler = require('moment');
SerialPort = require("serialport").SerialPort;
var serialPort;
var portName = '/dev/ttyACM0'; //change this to your Arduino port
var sendData = "";
var debug = false;
app.get('/', function(req, res){
res.sendFile(__dirname + '/public/interface.html')
});
socketServer.on('connection', function(socket){
console.log('a user connected');
socket.on('run', function(data){
serialPort.write('Z' + data + 'A');
console.log('write to ard');
console.log('Z' + data + 'A');
});
socket.on('stop', function(data){
serialPort.write('Y' + data + 'B');
console.log('write to ard');
console.log('Y' + data + 'B');
});
socket.on('configure', function(data){
serialPort.write('X' + data + 'C');
console.log('write to ard');
console.log('X' + data + 'C');
});
socket.on('temperatureValues', function(data){
serialPort.write(data);
console.log('write data to ard');
console.log(data);
});
socket.on('timeValues', function(data){
serialPort.write(data);
console.log('write data to ard');
console.log(data);
});
});
serialListener(debug);
function SocketIO_serialemit(sendData){
//console.log(sendData.length);
if(sendData.length >= 14)
{
var s_data = sendData.split(",");
socketServer.emit('temp1',{'temp': s_data[0]});
socketServer.emit('temp2',{'temp': s_data[1]});
socketServer.emit('temp3',{'temp': s_data[2]});
csv_stream.write(time_handler().format('HH:mm:ss') + ',');
csv_stream.write(s_data[0] + ',' + s_data[1] + ',' + s_data[2]);
csv_stream.write('\n');
//csv_stream.end();
}
else{
console.log("Error");
//var s_data = sendData.split(",");
//console.log(s_data[0]);
//console.log(s_data[1]);
//console.log(s_data[2]);
}
}
// Listen to serial port
function serialListener(debug)
{
var receivedData = "";
serialPort = new SerialPort(portName, {
baudrate: 9600,
// defaults for Arduino serial communication
dataBits: 8,
parity: 'none',
stopBits: 1,
flowControl: false
});
serialPort.on("open", function () {
console.log('open serial communication');
// Listens to incoming data
serialPort.on('data', function(data) {
if (data.toString() == "X")
{
console.log("Control Done");
socketServer.emit('Completed',{'key': data.toString()});
}
if (data.toString()[0] == "S")
{
console.log("Stage Done");
socketServer.emit('Stage',{'key': data.toString()[0]});
}
receivedData += data.toString();
//console.log(receivedData);
if (receivedData .indexOf('E') >= 0 && receivedData .indexOf('T') >= 0) {
sendData = receivedData .substring(receivedData .indexOf('T') + 1, receivedData .indexOf('E'));
receivedData = '';
SocketIO_serialemit(sendData);
}
});
});
}
http.listen(3000, function(){
console.log('listening on *:3000')
});
app.use(require('express').static(__dirname + '/public')); //sever static files (css, js, fonts, etc.)