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Client not receiving message from server

Hi i have a node js server and im using sockets to communicate.
Index:
<script src="socket.io/socket.io.js"></script>
Client JS:
var socket = io.connect("http://localhost:8081");
socket.on('hi', function(data){
console.log("g");
console.log(data);
});
So it seems to connect just fine to the server. I have a socket called 'hi' waiting for any incoming messages. I added 2 console logs incase data was null, it would still print something to the console.
Server:
var express = require("express");
var app = express();
var server = require("http").Server(app);
var io = require("socket.io")(server);
var mazeGenerator = require("generate-maze");
app.use(express.static("public"));
io.on("connection", function(socket) { // EDITED
console.log("A player has connected - sending maze data...");
socket.emit("hi", "hi");
});
So when i refresh the page, the client connects and in my CMD i see the "A player has connected..." console log. From then on, its blank from the server or client, I can keep refreshing and it will keep saying a player has connected by the clients console stays blank

Since the connection is proven to be established, I suspect this is an issue of a way you emit the data. Your second parameter hi may not be taken as a data to be transmitted, according to
https://socket.io/docs/server-api/#socket-emit-eventname-args-ack
In my understanding, socket.io emit Object instead of String so can you try this?
io.on("connection", function(socket) {
console.log("A player has connected - sending maze data...");
socket.emit("hi", {data: "hi"});
});

Socket.io—about socket disconnect

I have this scenario with socket.io:
I want to receive the data from a sever and Forward the data to webclient.But when I receive a lot of data and close the page, it console
DISCONNECTED FROM CLIENT
DISCONNECTED FROM CLIENT
DISCONNECTED FROM CLIENT
DISCONNECTED FROM CLIENT
DISCONNECTED FROM CLIENT
DISCONNECTED FROM CLIENT
DISCONNECTED FROM CLIENT
...(a lot)
Here is the code:
server:
var express=require('express');
var app=express();
var net=require('net');
var http=require('http').createServer(app);
var io=require('socket.io')(http);
var net=require('net');
var nodeServer = new net.Socket();
var aSocket=null;
io.on('connection', function (socketIO) {
aSocket=socketIO;
};
nodeServer.on('data', function(data) {
if(aSocket!=null){
aSocket.emit('pushToWebClient',useData);
aSocket.on('disconnect', function () {
console.log('DISCONNECTED FROM CLIENT');
});
}
client:
socket.on('pushToWebClient', function (useData) {
});
I find
aSocket.on('disconnect', function () {
console.log('DISCONNECTED FROM CLIENT');
});
console a lot of'DISCONNECTED FROM CLIENT' but actually it should console just once in the code.
I had even console.log(aSocket.id),it console just only one.
I don't know why it is console so many times.
I haved used setMaxListeners(10) to try to avoid it .
Will it lead to a memory leak？

It appears that you are registering multiple event listeners for the same disconnect event. In this code:
nodeServer.on('data', function(data) {
if(aSocket!=null){
aSocket.emit('pushToWebClient',useData);
aSocket.on('disconnect', function () {
console.log('DISCONNECTED FROM CLIENT');
});
}
You appear to be registering a new disconnect event listener every time you get a data message. So, if you have multiple listeners, then each one will get called when the socket disconnects and the result is that you will log the same message multiple times all for the same socket.
You can verify this is what is happening by moving your disconnect handler into the connection handler so it is only ever attached just once for each socket.
In addition putting asocket into a global or module-level variable means that your server code would only ever work with one single client at a time. It is not clear exactly what you are trying to do when you get data on the nodeserver connection - whether you're trying to send that data to only one specific client or to all connected clients.

I try to delete the code:
aSocket.on('disconnect', function () {
console.log('DISCONNECTED FROM CLIENT');
});
or moving it out of nodeServer handler,
it turn into normal and never suggest me to setMaxlisener.
I think maybe it is incorrect put one API into a API
And the envent maybe not release the socket,so it console multiple times .

EDIT: I'm moving this to the top because I saw that someone already provided my solution but you were having a problem managing the data sent to the client. Your aSocket variable will be overwritten by every new client that connects to your app. If you want to send data to a specific client using your server nodeServer, you should create a global variable (an array) that keeps track of all of your client socket connections. So instead of using one global variable aSocket do the following:
var net=require('net');
var nodeServer = new net.Socket();
var clients = [];
io.on('connection', function (socketIO) {
clients.push(socketIO);
var clientNum = clients.length-1;
aSocket.on('disconnect', function () {
clients.splice(clientNum, 1);
console.log('DISCONNECTED FROM CLIENT: '+socketIO.id);
});
};
nodeServer.on('data', function(data) {
//have your data object contain an identifier for the client that caused the handler to fire
//for the sake of the answer I just use data.id
var clientID = data.id;
if(clients[clientID]!=null){
clients[clientID].emit('pushToWebClient', useData);
}
}
Let me know how it goes! My original answer is below:
Try moving
aSocket.on('disconnect', function () {
console.log('DISCONNECTED FROM CLIENT');
});
out of your nodeServer.on('data', ...) event listener into the io.on('connection', ...) event listener like so:
io.on('connection', function (socketIO) {
aSocket=socketIO;
aSocket.on('disconnect', function () {
console.log('DISCONNECTED FROM CLIENT');
});
};
socket.io is designed to keep polling for the presence of the server/client. If either the server or the client are disconnected, the remaining 'side' continues to receive polling requests and, consequently, will continuously print an error.
You can see this effect on the client side in your browser when you disconnect your server and leave the client page open. If you look at the browser's error/console log what you should see is a continuous stream of net::ERR_CONNECTION_REFUSED errors. By placing the disconnect event handler in the .on('data', ...) handler for your server, you are seeing the converse of this situation.
net:ERR_CONNECTION_REFUSED example

This is basic code for socket.io
The following example attaches socket.io to a plain Node.JS HTTP
server listening on port 3000.
var server = require('http').createServer();
var io = require('socket.io')(server);
io.on('connection', function(client){
client.on('event', function(data){});
client.on('disconnect', function(){});
});
server.listen(3000);
I think, you should try.

Cannot emit socket message from client

So, I'm setting up an express app, with all the usual goodies like passport, mongoose, connect-flash etc, and I'm using socket.io to listen for and emit messages.
Currently, I'm just emitting messages to everyone (will be setting up rooms later on) and everything (but this) is working great. When an end user visits any page, all currently connected users receive a message "Hi everyone!", and the user who just connected obviously sends them self the message too. All as expected so far...
The issue:
I have a page that has a button on it...
<button id="register" type="button" class="btn btn-warning">Register</button>
When clicked, this should emit a message saying 'I want to register!' (currently to everyone but that doesn't matter yet). In response, the server should listen for this and respond by emitting a message back saying 'Hmmm, will think about it!'.
'registering' is never heard at the server, and so cannot emit the reply of 'registration-response'.
Can anyone see what I'm doing wrong?
I've seen this SocketIO, can't send emit data from client and a couple others that are similar but I am already doing what they have suggested :/
NB: The app is running on http://localhost:3000/ and the io using http://localhost:8678/events. If you need any further info just let me know
Client-side JS/jQuery (app.js)
var app = app || {};
app = (function($){
$(function () {
/////////////////////////////////////////////////////
// Connect to io and setup listeners
/////////////////////////////////////////////////////
var socket = io.connect('http://localhost:8678/events');
socket.on('connected', function (data) {
console.log(data); // Always see this in the console
});
socket.on('registration-response', function (data) {
console.log(data); // NOT seen in console
});
/////////////////////////////////////////////////////
// Setup click events
/////////////////////////////////////////////////////
$('#register').on('click', function(){
console.log('click'); // Always see this, so no binding issue
socket.emit('registering', 'I want to register!');
});
});
})(jQuery);
Server-side JS
var app = require('express');
var http = require('http');
var server = http.createServer(app);
var io = require('socket.io').listen(server); //pass a http.Server instance
server.listen(8678); //listen on port 8678
////////////////////////////////////////
// Register event listeners
////////////////////////////////////////
var events = io.of('/events');
events.on('connection', function(socket){ // This is heard and callback fires
events.emit('connected', 'Hi everyone!'); // This gets sent fine
});
events.on('registering', function(data){
events.emit('registration-response', 'Hmmm, will think about it!');
});

Your socket on the server isn't set up to listen for the event.
You need to do it like this
events.on('connection', function(socket){ // This is heard and callback fires
events.emit('connected', 'Hi everyone!'); // This gets sent fine
socket.on('registering', function(data){
events.emit('registration-response', 'Hmmm, will think about it!');
});
});
The socket now knows what to do when it receives the 'registering' event and will send the response to the '/events' namespace.

socket.io not emitting event from server to client on connection

I have a very basic setup with socket.io but am having trouble getting my server to send back a message once the connection has been established.
When a connection is established to my server, I want the server to send back a message to the client. I've tried to accomplish this with the following code:
Server
// Modules
var fs = require('fs');
var https = require('https');
// Certificate
var options = {
pfx: fs.readFileSync('<my cert>')
};
// Create Server
httpsServer = https.createServer(options);
// Create websocket
var io = require('socket.io')(httpsServer);
// Listen on a port
httpsServer.listen(4000,function() {
console.log('listening on *:4000');
});
io.on('connection', function(socket) {
console.log('a user connected');
socket.emit('test','you connected');
});
Client
var socket = io('https://<my server>:4000');
When I execute this code, the websocket gets established and my server console shows the message "a user connected". However, the message ['test','you connected'] does not get emitted through the socket.
The only way I've been able to get this to work is to use setTimeout() to wait 500ms before emitting the event, in which case it does work.
Why is that? How can I configure my server to automatically respond with a message as soon as the user connects?

You need to listen to the emitted event, using socket.on(event, callback);
<script src="https://cdn.socket.io/socket.io-1.4.5.js"></script>
<script>
var socket = io('https://localhost:4000');
//test is the emitted event.
socket.on("test", function(data){
console.log(data); //"you connected"
});
</script>

How to emit an event in response to an event using socket.io?

I am new to socket.io, and trying to get it to work. I don't know what I am doing wrong here, as it seems super straightforward - yet it is not working. I suppose I am missing something obvious. Hopefully someone else can see what that is.
I am setting up socket.io to work with a node/express server. Here is a simplified version of the test I am trying to do.
Server:
var http = require('http');
var express = require('express');
var app = express();
var server = http.createServer(app);
var io = require('socket.io')(server);
/* socket.io test */
io.on('connection', function(socket){
socket.on('helloServer', function(clientMessage){
console.log("Server got 'helloServer' event");
socket.emit('helloClient', { message : "Hi there. We got your message: " + clientMessage.message});
});
});
The client has a function callServer that is called when a user clicks a button in the UI:
var socket = io.connect('http://localhost');
function callServer() {
socket.emit('helloServer', { message : "Hello server!" });
}
socket.on('helloClient', function (serverMessage) {
console.log(serverMessage.message);
});
When I run this code, and click the button that calls callServer, the server does get the event, helloServer, because I see that the console logs the message as expected, but the client never receives a helloClient event. It is as if the socket.emit call within the socket.on response function never gets called.
What am I doing wrong?

It appears to be ok. But, just in case, check this answer with all ways of sending data to clients and try use "io.emit" (to send to all clients). Or try sending a string instead of a json object.
I have tried this example here and it is working, just copied and pasted.