Develop Reference

Why does "WebRTC Screen sharing" is not streaming when using different computers?

I am developing a web application, like an online classroom in which I want to share the screen of a browser from a computer and view it in another. I am getting an error "Uncaught (in promise) DOMException: Error" in chrome when I tried to share the screen from a computer and view it on another computer.
I am using WebRTC for this and WebSocket for signaling. At the backend, java jersey would be doing the searching & forwarding of the request to the appropriate clients. I can share the screen from one browser window and view it in another on the same machine. But when I'm using different computers I get this error. When I debug the RTCPeerConnection object, it shows that the property connectionState as failed and iceConnectionState as disconnected.
Javascript: Request to share the screen
var urlS = [];
var config = {iceServers: urlS};
var $source = $('#monitor-src');
$scope.context.peerConnection = new RTCPeerConnection();
$scope.context.peerConnection.onicecandidate = function(event)
{
console.log(event)
if (event.candidate)
{
var json =
{
type:event.type,
label:event.candidate.sdpMLineIndex,
id:event.candidate.sdpMid,
candidate:event.candidate
}
WebSocket.send({desc:json,usrId:$scope.context.me.id},$scope)
}
else
{
console.error("Failed to create ice candidate")
}
};
try
{
$scope.context.peerConnection.createOffer({offerToReceiveAudio: true,offerToReceiveVideo: true}).then(function(offer)
{
return $scope.context.peerConnection.setLocalDescription(offer);
}).then(function()
{
WebSocket.send({desc:$scope.context.peerConnection.localDescription,callee:mentee.id,caller:$scope.context.me.id,usrId:$scope.context.me.id},$scope)
});
}
catch(error)
{
console.error("onnegotiationneeded-"+error)
}
$scope.context.peerConnection.onnegotiationneeded = function()
{
console.error("onnegotiationneeded")
};
try
{
console.log($scope.context.peerConnection);
$scope.context.peerConnection.ontrack = function(event)
{
console.log("ontrack:"+event.streams.length)
$source.parent()[0].srcObject= event.streams[0];
};
$scope.context.peerConnection.onaddstream = function(event)
{
console.log("onaddstream:"+event.stream)
$source.parent()[0].srcObject = event.stream;
};
}
catch(error)
{
console.error(error)
}
Javascript:WebSocket Handling of the request and sending response
$rootScope.socket.onMessage(function(message)
{
data = angular.fromJson(message.data);
if(data.type == 'offer')
{
var stream = null;
//var urlS = [{urls: 'stun:192.168.1.16:8443'}];
var urlS = [];
var config = {iceServers: urlS};
scope.context.peerConnection = new RTCPeerConnection();
scope.context.peerConnection.setRemoteDescription(data).then(function(){
return navigator.mediaDevices.getDisplayMedia({video:true,audio: true});
}).then(function(stream){
console.log(scope.context.peerConnection)
scope.context.peerConnection.addStream(stream);
stream.getTracks().forEach(function(track)
{
//var rtpSender =
});
scope.context.peerConnection.createAnswer().then(function(answer){
return scope.context.peerConnection.setLocalDescription(answer)
}).then(function()
{
send({desc:scope.context.peerConnection.localDescription,usrId:scope.context.me.id},scope)
}).catch(function(error){
console.error(error)});
})
}
else if(data.type == 'answer')
{
scope.context.peerConnection.setRemoteDescription(data);
}
else if(data.type == 'icecandidate')
{
console.log("icecandidate:"+angular.toJson(data))
var promise = scope.context.peerConnection.addIceCandidate(data.candidate).then(function success(){
console.log("ice success")
}).catch(function error(err)
{
console.log(err);
});
}
});
};
The ontrack and onaddstream events are triggered when a stream is added to the peer connection. But I get nothing on the requested peer.

I am not a JavaScript expert but your urlS array seems to be empty. Try to add both Turn and Stun servers in your urlS.
For more info take a look here

TypeError: serialport.parsers.readline is not a function

I am trying to run this program in Raspberry Pi 3.
I have installed nodejs and ws on my raspberry pi.
Then I installed serial port module.
I am trying to create this project:enter link description here
I have tried to find solutions everywhere but I could not find one.
If any one knows how to solve this problem please help me.
var webSocketUrl = "wss://api.artik.cloud/v1.1/websocket?ack=true";
var device_id = "5bb3ba9304674086bee67fa507a215cf"; //DEVICE ID
var device_token = "36b278345b6d4d11abf764ae213c5c70"; //DEVICE TOKEN
var WebSocket = require('ws');
var isWebSocketReady = false;
var data="";
var ws = null;
var serialport = require("serialport");
var SerialPort = serialport.SerialPort;
var sp = new SerialPort("/dev/ttyACM0", { //for serial communication with arduino
baudrate: 9600,
// The baud rate of uno is 9600
parser: serialport.parsers.readline("\n")
});
/**
* Gets the current time in millis
*/
function getTimeMillis(){
return parseInt(Date.now().toString());
}
/**
* Create a /websocket connection and setup GPIO pin
*/
function start() {
//Create the WebSocket connection
isWebSocketReady = false;
ws = new WebSocket(webSocketUrl);
ws.on('open', function() {
console.log("WebSocket connection is open ....");
register();
});
ws.on('message', function(data) {
//this loop is called whenever the client sends some message
handleRcvMsg(data); //data is send to the function handleRcvMsg()
});
ws.on('close', function() {
console.log("WebSocket connection is closed ....");
});
}
/**
* Sends a register message to /websocket endpoint
*/
//Client will only work when device gets registered from here
function register(){
console.log("Registering device on the WebSocket connection");
try{
var registerMessage = '{"type":"register", "sdid":"'+device_id+'", "Authorization":"bearer '+device_token+'", "cid":"'+getTimeMillis()+'"}';
console.log('Sending register message ' + registerMessage + '\n');
ws.send(registerMessage, {mask: true});
isWebSocketReady = true;
}
catch (e) {
console.error('Failed to register messages. Error in registering message: ' + e.toString());
}
}
//data after receiving is sent here for processing
function handleRcvMsg(msg){
var msgObj = JSON.parse(msg);
if (msgObj.type != "action") return; //Early return;
var actions = msgObj.data.actions;
var actionName = actions[0].name; //assume that there is only one action in actions
console.log("The received action is " + actionName);
}
/**
* Send one message to ARTIK Cloud
*/
//This function is responsible for sending commands to cloud
//function sendStateToArtikCloud(parking,temperature,water){
function sendDataToArtikCloud(pantry){
var result=pantry.split(" ");//data gets split by " " to get the values
try{
ts = ', "ts": '+getTimeMillis();
var data = {
"Garlic": result[1],
"Potato":result[2],
"Temperature":result[3],
"Chilli":result[4],
"Humidity": result[5],
"Ginger":result[6],
"Onion": result[7]
};
var payload = '{"sdid":"'+device_id+'"'+ts+', "data": '+JSON.stringify(data)+', "cid":"'+getTimeMillis()+'"}';
console.log('Sending payload ' + payload + '\n');
ws.send(payload, {mask: true});
} catch (e) {
console.error('Error in sending a message: ' + e.toString() +'\n');
}
}
function exitClosePins() {
console.log('Exit and destroy all pins!');
process.exit();
}
start();
//exectes every second when data is received from arduino (5sec programmed delay from arduino)
sp.on("open", function () {
sp.on('data', function(data) {
console.log("Serial port received data:" + data);
//var result=data.split(" ");//data gets split by " " to get the values
//sendStateToArtikCloud(result[0],result[2],result[1]);//parking,temperature,waterlevel
sendDataToArtikCloud(data);
});
});
process.on('SIGINT', exitClosePins);
I am getting an error on my raspberry pi
enter image description here
Suggest me a solution.

The documentation will tell you that Readline is spelled with a capital R
https://www.npmjs.com/package/serialport#module_serialport--SerialPort.parsers
parser: serialport.parsers.Readline("\n")
~

[TypeError: serialport.parsers.readline is not a function.]
If it has not been resolved yet, try this method.
var serialport = require("serialport")
var SerialPort = serialport.SerialPort;
var sp = new serialport("/dev/ttyACM0"),{
BaudRate: 9600,
parser: new serialport.parsers.Readline("\r\n")
});
I hope your problem is solved.

How to start a Server-Sent Event "only once" inside a SharedWorker to push message for any open script?

I have a server-sent event (SSE) implementation that is working with almost no issues. The only issue that I am having is "one user can have many connections to the server". Basically, If a user opens more than one web browser's tab, each tab will create a brand new server-sent event request to the server which cause many requests to run from a single user.
To solve this problem, I would like to run the SSE inside a Javascript's SharedWorker.
This means that I have only one SSE communicating with a SharedWorker. Then, every page/web browser will communication with the SharedWorker. This gives me the advantage of only allowing one SSE per user.
This is how my SSE working currently without any type of worker.
$(function(){
//connect to the server to read messages
$(window).load(function(){
startPolling( new EventSource("poll.php") );
});
//function to listen for new messages from the server
function startPolling(evtSource){
evtSource.addEventListener("getMessagingQueue", function(e) {
var data = JSON.parse(e.data);
//handle recieved messages
processServerData(data);
}, false);
evtSource.onerror = function(e) {
evtSource.close();
};
}
});
I would like to have the same setup running. However, I would like to run it inside a javascript's SharedWorker to eliminate having more than one SSE per user.
I am struggling to implement the SharedWorker. Here is what I tried so far
I created a file called worker.js and added this code to it
var ports = [] ;
onconnect = function(event) {
var port = event.ports[0];
ports.push(port);
port.start();
var serv = new EventSource(icwsPollingUrl)
serv.addEventListener("getMessagingQueue", function(e) {
var data = JSON.parse(e.data);
processServerData(data);
}, false);
}
Then on the page where I want to listed to messages I have this code
$(function(){
$(window).load(function(){
var worker = new SharedWorker("worker.js");
worker.port.start();
worker.port.onmessage = function(e) {
console.log(e.data);
console.log('Message received from worker');
}
});
});
What am I missing here?
What am I doing wrong?
How can I correct the implementation?
EDITED
Based on the comments below from #Bergi, here is an updated version of my implementation which is still not posting messages to the connectors. I added comments to my code explaining understanding of what is going on with the code.
On a landing page i.e. index.php I connect to my SharedWorker like this
$(function($){
//establish connection to the shared worker
var worker = new SharedWorker("/add-ons/icws/js/worker1.js");
//listen for a message send from the worker
worker.port.addEventListener("message",
function(event) {
console.log(event.data);
}
, false
);
//start the connection to the shared worker
worker.port.start();
});
This is the code as my worker1.js file contains
var ports = [] ;
//runs only when a new connection starts
onconnect = function(event) {
var port = event.ports[0];
ports.push(port);
port.start();
//implement a channel for a communication between the connecter and the SharedWorker
port.addEventListener("message",
function(event) {
listenForMessage(event, port);
}
);
}
//reply to any message sent to the SharedWorker with the same message but add the phrase "SharedWorker Said: " to it
listenForMessage = function (event, port) {
port.postMessage("SharedWorker Said: " + event.data);
}
//runs every time and post the message to all the connected ports
function readNewMessages(){
var serv = new EventSource(icwsPollingUrl)
serv.addEventListener("getMessagingQueue", function(e) {
var queue = JSON.parse(e.data);
notifyAllPorts(queue);
}, false);
}
//check all open ports and post a message to each
function notifyAllPorts(msg){
for(i = 0; i < ports.length; i++) {
ports[i].postMessage(msg);
}
}
Here is one more version of my worker1.js
var ports = [] ;
//runs only when a new connection starts
onconnect = function(event) {
var port = event.ports[0];
ports.push(port);
port.start();
//implement a channel for a communication between the connecter and the SharedWorker
port.addEventListener("message",
function(event) {
listenForMessage(event, port);
}
);
}
//reply to any message sent to the SharedWorker with the same message but add the phrase "SharedWorker Said: " to it
listenForMessage = function (event, port) {
port.postMessage("SharedWorker Said: " + event.data);
}
readNewMessages();
//runs every time and post the message to all the connected ports
function readNewMessages(){
console.log('Start Reading...');
var serv = new EventSource(icwsPollingUrl);
serv.addEventListener("getMessagingQueue", function(e) {
var queue = JSON.parse(e.data);
console.log('Message Received');
console.log(queue);
notifyAllPorts(queue);
}, false);
}
//check all open ports and post a message to each
function notifyAllPorts(msg){
for(i = 0; i < ports.length; i++) {
ports[i].postMessage(msg);
}
}

maybe is late but you can create a EventSource singleton in the worker like this:
let ports = [];
var EventSourceSingleton = (function () {
var instance;
function createInstance() {
var object = new EventSource('your path');
return object;
}
return {
getInstance: function () {
if (!instance) {
instance = createInstance();
}
return instance;
}
};
})();
onconnect = function(e) {
var port = e.ports[0];
ports.push(port);
var notifyAll = function(message){
ports.forEach(port => port.postMessage(message));
}
var makeConnection = function (){
var source = EventSourceSingleton.getInstance();
source.onopen = function (e){
var message = "Connection open"
port.postMessage(message);
}
source.onerror = function(e){
var message ="Ups you have an error";
port.postMessage(message);
}
source.onmessage = function(e){
// var message = JSON.parse(event.data);
notifyAll(e.data);
}
}
port.onmessage = function(e) {
makeConnection();
}
port.start();
}
And you can call it from outside like this.
var shWorker = new SharedWorker('woker.js');
shWorker.port.onmessage = function (e) {
console.log('Message received from worker');
setmsj(e.data);
}
//Dummy message - For initialize
shWorker.port.postMessage(true);
Have fun debuggin this on // chrome://inspect/#workers.

OnMessage event never getting called - Websockets client (javascript)

I am having trouble writing a client to establish a web socket connection. The client successfully establishes a connection but when the server sends data the OnMessage event never gets triggered. I am using OWIN Websocket Extension for my server side portion.
Server
dynamic data = fillData(value);
string sendInfo = Newtonsoft.Json.JsonConvert.SerializeObject(data);
byte[] infoBytes = System.Text.Encoding.UTF8.GetBytes(sendInfo);
await sendAsync(new ArraySegment<byte>(infoBytes), 1, false, pair.Key.callCancelled);
Client
try {
url = "wss://localhost/piwebapi/elements/E0DqD5loBNH0erqeqJodtALA2U5w0WX-5BGAupiQlq51PAUkVTVFVOSVRcU1VHQVJNQU5cU0FNUExFIEVMRU1FTlQ/attributes";
socket = new WebSocket(url);
socket.onopen = function (openEvent) {
document.getElementById("serverStatus").innerHTML =
'WebSocket Status:: Socket Open';
document.getElementById("destination").innerHTML =
url;
};
socket.onmessage = function (messageEvent) {
if (messageEvent.data instanceof Blob) {
var destinationCanvas = document.getElementById('destination');
var destinationContext = destinationCanvas.getContext('2d');
var image = new Image();
image.onload = function () {
destinationContext.clearRect(0, 0,
destinationCanvas.width, destinationCanvas.height);
destinationContext.drawImage(image, 0, 0);
}
image.src = URL.createObjectURL(messageEvent.data);
} else {
document.getElementById("serverResponse").innerHTML =
'Server Reply:: ' + messageEvent.data;
}
};
socket.onerror = function (errorEvent) {
document.getElementById("serverStatus").innerHTML =
'WebSocket Status:: Error was reported';
};
socket.onclose = function (closeEvent) {
document.getElementById("serverStatus").innerHTML =
'WebSocket Status:: Socket Closed';
};
}
catch (exception) { if (window.console) console.log(exception); }
The OnOpen and OnClose work just fine but somehow the OnMessage never gets triggered, any ideas?
Edit - Sending data from client to server works as well.

How do I close a sockjs connection on the server side?

So, every time I refresh the page, it seems like sockjs is creating a new connection.
I am saving every message to my mongodb on every channel.onmessage, so if I refresh my page 7 times and send a message, I would save 7 messages of the same content into my mongodb.
This is very problematic because when I retrieve those messages when I go into the chat room, to see the log, I would see bunch of duplicate messages.
I want to keep track of all connections that are 'active', and if a user tries to make another connections, I want to be able to force close on the old one from the server side, so there is only 1 connection listening to each message at a time
How do I do this ?
var connections = {};
//creating the sockjs server
var chat = sockjs.createServer();
//installing handlers for sockjs server instance, with the same url as client
chat.installHandlers(server, {prefix:'/chat/private'});
var multiplexer = new multiplexServer.MultiplexServer(chat);
var configChannel = function (channelId, userId, userName){
var channel = multiplexer.registerChannel(channelId);
channel.on('connection', function (conn) {
// console.log('connection');
console.log(connections);
connections[channelId] = connections[channelId] || {};
if (connections[channelId][userId]) {
//want to close the extra connection
} else {
connections[channelId][userId] = conn;
}
// }
// if (channels[channelId][userId]) {
// conn = channels[channelId][userId];
// } else {
// channels[channelId][userId] = conn;
// }
// console.log('accessing channel! ', channels[channelId]);
conn.on('new user', function (data, message) {
console.log('new user! ', data, message);
});
// var number = connections.length;
conn.on('data', function(message) {
var messageObj = JSON.parse(message);
handler.saveMessage(messageObj.channelId, messageObj.user, messageObj.message);
console.log('received the message, ', messageObj.message);
conn.write(JSON.stringify({channelId: messageObj.channelId, user: messageObj.user, message: messageObj.message }));
});
conn.on('close', function() {
conn.write(userName + ' has disconnected');
});
});
return channel;
};

Simply use .close:
if (connections[channelId][userId]) {
// want to close the extra connection
connections[channelId][userId].close();
} else {
connections[channelId][userId] = conn;
}