Develop Reference

Web Serial API crashes Zebra DS9208 on initial connection

I am attempting to use a Zebra DS9208 scanner to capture barcode data into a web page. For some reason, when I first select the serial port and connect to the scanner, the very first scan causes the barcode reader to crash (it locks into read mode, refuses to read additional scans, then disconnects from the computer and reboots itself). When I establish the connection a second time, the scanner continuously reads scans without issues. Anyone able to spot anything in my code that could cause this?
Connect Script:
async function connect() {
// - Request a port and open a connection.
port = await navigator.serial.requestPort();
// - Wait for the port to open.
await port.open({ baudRate: 9600 });
// Send a bunch of Bell characters so we can hear that the scanner understands us.
await quadBeep();
// Read the stream let textDecoder = new TextDecoderStream();
inputDone = port.readable.pipeTo(textDecoder.writable);
reader = textDecoder.readable.getReader();
readScans();
}
Beep Script (used to make the scanner beep by sending a BELL character)
function quadBeep() {
console.log('Quad Beep Requested');
//Write to output stream
const writer = port.writable.getWriter();
const data = new Uint8Array([07, 07, 07, 07]);
writer.write(data);
//allow the serial port to be closed later
writer.releaseLock();
return;
}
Read Loop to source data from the scanner:
`async function readScans() {
//Listen to data coming from the serial device
async function readScans() {
while (true) {
try {
const { value, done } = await reader.read();
await saveScan(value); //process the scan
console.log('readScans Barcode: ' + value);
document.getElementById('scan').innerHTML += value;
if (done) {
//Allow the serial port to be closed later.
console.log('readScans done value: ' + done);
reader.releaseLock();
break;
}
} catch(error) {
console.log('readScans Error: ' + error);
break;
}
}
}
Save Function, to write the data (eventually will submit the barcode via AJAX)
function saveScan(barcode) {
var session = document.getElementById('sessionID').getAttribute('data-value');
if (barcode == previousBarcode) {
//duplicate scan.
console.log('saveScan Duplicate');
return;
} else {
//Submit the scan
previousBarcode = barcode; //store the barcode so it doesn't get rescanned
console.log('saveScan Previous set to: ' + barcode);
//future AJAX FUNCTION GOES HERE
return;
}
}

How to access input/output of worklet node from main file?

I have created a real time voice chat application for a game I am making. I got it to work completely fine using audiocontext.createScriptProcessor() method.
Here's the code, I left out parts that weren't relevant
//establish websocket connection
const audioData = []
//websocket connection.onMessage (data) =>
audioData.push(decodeBase64(data)) //push audio data coming from another player into array
//on get user media (stream) =>
const audioCtx = new AudioContext({latencyHint: "interactive", sampleRate: 22050,})
const inputNode = audioCtx.createMediaStreamSource(stream)
var processor = audioCtx.createScriptProcessor(2048, 1, 1);
var outputNode = audioCtx.destination
inputNode.connect(tunerNode)
processor.connect(outputNode)
processor.onaudioprocess = function (e) {
var input = e.inputBuffer.getChannelData(0);
webSocketSend(input) //send microphone input to other sockets via a function set up in a different file, all it does is base 64 encode then send.
//if there is data from the server, play it, else, play nothing
var output
if(audioData.length > 0){
output = audioData[0]
audioData.splice(0,1)
}else output = new Array(2048).fill(0)
};
the only issue is that the createScriptProccessor() method is deprecated. As recommended, I attempted to do this using Audio Worklet Nodes. However I quickly ran into a problem. I can't access the user's microphone input, or set the output from the main file where the WebSocket connection is.
Here is my code for main.js:
document.getElementById('btn').onclick = () => {createVoiceChatSession()}
//establish websocket connection
const audioData = []
//webSocket connection.onMessage (data) =>
audioData.push(data) //how do I get this data to the worklet Node???
var voiceChatContext
function createVoiceChatSession(){
voiceChatContext = new AudioContext()
navigator.mediaDevices.getUserMedia({audio: true}).then( async stream => {
await voiceChatContext.audioWorklet.addModule('module.js')
const microphone = voiceChatContext.createMediaStreamSource(stream)
const processor = new AudioWorkletNode(voiceChatContext, 'processor')
microphone.connect(processor).connect(voiceChatContext.destination)
}).catch(err => console.log(err))
}
Here is my code for module.js:
class processor extends AudioWorkletProcessor {
constructor() {
super()
}
//copies the input to the output
process(inputList, outputList) { // how do I get the input list data (the data from my microphone) to the main file so I can send it via websocket ???
for(var i = 0; i < inputList[0][0].length; i++){
outputList[0][0][i] = inputList[0][0][i]
outputList[0][1][i] = inputList[0][1][i]
}
return true;
}
}
registerProcessor("processor", processor);
So I can record and process the input, but I can't send input via WebSocket or pass in data that is coming from the server to the worklet node because I can't access the input list or output list from the main file where the WebSocket connection is. Does anyone know a way to work around this? Or is there a better solution that doesn't use audio worklet nodes?
Thank you to all who can help!

I figured it out, all I needed to do was use the port.onmessage method to exchange data between the worklet and the main file.
processor.port.onmessage = (e) => {//do something with e.data}

IBM MQ How read one by one message, not all available in a queue manager at once?

Now, my app receives all available messages in a Queue manager. I collect them locally and process one by one.
Could do I configure it to receive one message, do some work (it can take some time), delete the received message, repeat? Is this behavior possible with IBM MQ?
The code was updated
function listenToMQ() {
const qMgr = inbound.queueManagerName;
const qName = inbound.queueName;
const connName = inbound.host;
const cno = new mq.MQCNO();
const sco = new mq.MQSCO();
const csp = new mq.MQCSP();
const cd = new mq.MQCD();
cno.SecurityParms = csp;
csp.UserId = inbound.userID;
csp.authenticationType = 0;
cno.Options |= MQC.MQCNO_CLIENT_BINDING;
cd.ConnectionName = connName;
cd.ChannelName = inbound.channelName;
cd.SSLClientAuth = MQC.MQSCA_OPTIONAL;
cd.MaxMsgLength = 104857600;
cno.ClientConn = cd;
cno.SSLConfig = sco;
mq.setTuningParameters({
syncMQICompat: true });
mq.Connx(qMgr, cno, function(err, hConn) {
if (err) {
logger.errorLogger().error(err.message);
} else {
const od = new mq.MQOD();
od.ObjectName = qName;
od.ObjectType = MQC.MQOT_Q;
const openOptions = MQC.MQOO_BROWSE;
mq.Open(hConn, od, openOptions, function(err, hObj) {
queueHandle = hObj;
if (err) {
logger.errorLogger().error(err.message);
} else {
getMessages();
}
});
} }); }
function getMessages() {
const md = new mq.MQMD();
const gmo = new mq.MQGMO();
gmo.Options =
MQC.MQGMO_NO_SYNCPOINT |
MQC.MQGMO_MQWI_UNLIMITED |
MQC.MQGMO_CONVERT |
MQC.MQGMO_FAIL_IF_QUIESCING;
gmo.Options |= MQC.MQGMO_BROWSE_FIRST;
gmo.MatchOptions = MQC.MQMO_NONE;
mq.setTuningParameters({
getLoopPollTimeMs: 500 }); mq.Get(queueHandle, md, gmo, getCB); }
function getCB(err, hObj, gmo, md, buf, hConn) {
if (md.Format == "MQSTR") {
console.log(md);
const message = decoder.write(buf);
updateDB(getMetaFeed(message));
}
mq.Cmit(hConn);
}
gmo.Options &= ~MQC.MQGMO_BROWSE_FIRST;
gmo.Options |= MQC.MQGMO_BROWSE_NEXT; }

Yes, most certainly you can.
Your application can get one message, perhaps using syncpoint if it is a message that drives some work that needs done, do the work and then when the work is done commit the get of the message and then go and get the next one. If the work that needs to be done is also transactional (e.g. update a database), then a global transaction could be used to commit both the MQ message and the update of the other transactional resource at the same time.
The code you show in your question appears to be doing a browse of messages (queue opened with MQOO_BROWSE and then messages read using MQGMO_BROWSE_FIRST and then MQGMO_BROWSE_NEXT). I'm not sure how or when your application currently removes the messages from the queue?
Your current code appears to be processing the messages one by one already, so the only changes needed would be to the get options (and to add a commit call).

socket.io code organizing and timing ES6

i have an experimental app that is pretty simple, you click a display button and an image appears in real time to all clients, utilizing socket.io. now it does work for the most part. however i had an issue (my original question here: socket.io emit on connect) with an event not happening when the client connected, but i have resolved it with the help of this thread: socket.emit on sever side is ignored after connection?.
basically, my 'new-client-append event' retrieves data (html in the form of a string) so that when a new client connects, it shows the same data that current clients see (similar to connecting to a chat room and being able to see all chat history). i had to reorganize my code so my 'new-client-append' event would take place, and i can get it to work if i put data in manually. my new issue is now that i have had to reorganize my code, my 'new-client-append' event is dependent on a variable i set within the class, so it is no longer recognizable. i'm relatively new to JS, how can i get my variable to be recognized and why is this happening? i had tried moving the event in different places of my code with no luck. it is the this.mainContainer variable.
CLIENT
import $ from 'jquery';
import SaveInput from './SaveInput';
import io from 'socket.io-client';
// make connection
const socket = io.connect('localhost:3000');
**socket.on('new-client-append', (data) => {
console.log('NEW CLIENT ENTERED');
console.log('on new-client-clone ' + JSON.stringify(data));
this.mainContainer.append(data);
});**
socket.on('connect_error', function(){
console.log('fail');
});
class Display extends SaveInput {
constructor(){
this.mainContainer = $('.main-container');
this.pGrid = $('.pic-grid-container');
this.display = $('#btn-display');
this.buttons();
}
buttons (){
// click buttons
this.display.click(this.displayEls.bind(this));
//display images
displayEls() {
let img = 'https://secure.gravatar.com/avatar/22f38e0216f57af53a1776fb2a72c436?s=60&d=wavatar&r=g';
let $picContainer = $('<div class="picture-frame"></div>');
let $newImg = $('<img>');
// clone pic-grid-container
let htmlClone = this.pGrid.clone();
let stringClone = htmlClone.html();
// EMIT
//send image url
socket.emit('client-image', {
image: img
});
// send dom clone to server
socket.emit('new-client-append', {
clone: stringClone
});
// LISTEN
// append image in real time
socket.on('client-image', (data) => {
let foo = data.image.toString();
$newImg.attr('src', foo);
// console.log(data);
// console.log(foo);
$newImg.appendTo($picContainer);
this.pGrid.append($picContainer);
// console.log('html clone ' + JSON.stringify(htmlClone));
// console.log('string clone ' + stringClone);
});
}
export default Display;
SERVER
const express = require('express');
const socketIO = require('socket.io');
const http = require('http');
// app set up
const app = express();
const server = http.Server(app);
// const = new socket(server);
let port = process.env.PORT || 3000;
// static files
app.use(express.static('app'));
// socket setup & pass SERVER
const io = new socketIO(server);
let jqueryImage;
// on client connect
io.on('connection', (socket) => {
console.log('client has entered...');
socket.emit('new-client-append', jqueryImage);
// events
socket.on('client-image', function(data){
console.log('SERVER ' + data.image);
io.sockets.emit('client-image', data);
});
socket.on('new-client-append', function(data){
jqueryImage = data.clone;
console.log('jqueryImage ' + JSON.stringify(jqueryImage));
});
// errors
io.on('error', function (err) {
console.log(err);
});
io.on('connect_error', function(){
console.log('fail');
});
});
server.listen(port, () => {
console.log('server running....');
});
UPDATE
added suggested code, calling the maincontainer from the display object. but it is saying that it is not defined.
socket.on('new-client-append', (data) => {
console.log('NEW CLIENT ENTERED');
console.log('on new-client-clone ' + JSON.stringify(data));
**display.mainContainer.append(data);**
});
file where i create the objects
import SaveInput from './modules/SaveInput';
import Display from './modules/Display';
const saveInput = new SaveInput();
const display = new Display ();

Your socket.on function has
this.mainContainer.append(data);
This implies that you've attached a mainContainer property to the socket object. Because you've not done this, but rather declared it inside your Display (sub)class, it's attached to the Display object you created.. I can't seem to find it, but somewhere, wherever this script is required there is a
variable = new Display();
You must call this mainContainer object by it's name. Find that code that initiates the Display object and then use
theVarNameYouFound.mainContainer.append(thatThing);

How to pass socket to cluster in node

I would like to get a multi-process node. Workers are listening clients connections. I need pass sockets to master process because master process emit message to clients. Workers also need socket to emit message to clients.
Socket is a circular object and can't pass to a master process.
My code:
const cluster = require('cluster');
const http = require('http');
var io = require('socket.io');
var users;
var clients = {};
if (cluster.isMaster) {
function messageHandler(msg) {
if (msg.usersarray) {
usersarray = msg.usersarray;
console.log(usersarray);
}else if(msg.socket){
clients[usersarray["manu"][0]] = msg.socket;
clients[usersarray["manu"][0]].emit("hola","hola");
}
}
// Start workers and listen for messages containing notifyRequest
const numCPUs = require('os').cpus().length;
for (var i = 0; i < numCPUs; i++) {
cluster.fork();
}
Object.keys(cluster.workers).forEach((id) => {
cluster.workers[id].on('message', messageHandler);
});
}else {
// Create server & socket
var server = http.createServer(function(req, res){
// Send HTML headers and message
res.writeHead(404, {'Content-Type': 'text/html'});
res.end('<h1>Aw, snap! 404</h1>');
});
server.listen(3000);
io = io.listen(server);
// Add a connect listener
io.sockets.on('connection', function(socket) {
var hs = socket.handshake;
console.log("socket connected");
if(users == undefined){
users = {};
}
if(hs.query.usuario != undefined){
if(users[hs.query.usuario] == undefined){
users[hs.query.usuario] = new Array();
}
users[hs.query.usuario].push(socket.id); // connected user with its socket.id
clients[socket.id] = socket; // add the client data to the hash
process.send({ usersarray: users});
process.send({ socket: socket});
}
// Disconnect listener
socket.on('disconnect', function() {
console.log('Client disconnected.');
});
});
}
in line process.send({ socket: socket}); Node js get error "TypeError: Converting circular structure to JSON"
-I used some module to transform circular object but don't working.
-I tried to pass socket id and then in master process, created new socket with this id but I didn't know to use it.
There is any posibility to pass socket from worker to master process?
Node js version: v5.5.0

Hm, I don't think it is possible what you are trying to do. When you create a cluster it means that you create separate processes (master + workers) which can only talk over the pipe.
Talking over the pipe means they can only send strings to each other. process.send tries to serialize a Javascript object as JSON (--> making a string out of it) using JSON.stringify. JSON for example cannot have functions, circles, etc. I just checked the socket object, it is very complex and contains functions (such as socket.emit()), so you cannot just serialize it and send it over the pipe.
Maybe you can check this or this on how to use clustered WebSockets.
It doesn't seem very trivial.. Maybe you can just pass CPU intensive tasks to some worker processes (via cluster or just spawning them yourself), send the results back to the master and let him do all the communication with the client?

I understand your purpose of broadcasting to all the node worker processes in a cluster, although you can not send socket component as such but there is a workaround for the purpose to be served. I will try an explain with an example :
Step 1: When a client action requires a broadcast :
Child.js (Process that has been forked) :
socket.on("BROADCAST_TO_ALL_WORKERS", function (data)
{
process.send({cmd : 'BROADCAST_TO_ALL_WORKERS', message :data.message});
})
Step 2: On the cluster creation side
Server.js (Place where cluster forking happens):
if (cluster.isMaster) {
for (var i = 0; i < numCPUs; i++) {
var worker = cluster.fork();
worker.on('message', function (data) {
if (data.cmd === "BROADCAST_TO_ALL_WORKERS") {
console.log(server_debug_prefix() + "Server Broadcast To All, Message : " + data.message + " , Reload : " + data.reload + " Player Id : " + data.player_id);
Object.keys(cluster.workers).forEach(function(id) {
cluster.workers[id].send({cmd : "BROADCAST_TO_WORKER", message : data.message});
});
}
});
}
cluster.on('exit', function (worker, code, signal) {
var newWorker = cluster.fork();
newWorker.on('message', function (data) {
console.log(data);
if (data.cmd === "BROADCAST_TO_ALL_WORKERS") {
console.log(data.cmd,data);
Object.keys(cluster.workers).forEach(function(id) {
cluster.workers[id].send({cmd : "BROADCAST_TO_WORKER", message : data.message});
});
}
});
});
}
else {
//Node Js App Entry
require("./Child.js");
}
Step 3: To Broadcast in the child process
-> Put this before io.on("connection") in Child.js
process.on("message", function(data){
if(data.cmd === "BROADCAST_TO_WORKER"){
io.sockets.emit("SERVER_MESSAGE", { message: data.message, reload: data.reload, player_id : data.player_id });
}
});
I hope its clear. Please comment if its confusing ... I will try and make it clear.