The NodeJS socket.io server is not responding - node.js

Question

You can see for yourself that the request hangs:
curl "http://europasprak.com:9001/socket.io/?EIO=4&transport=polling"
It also hangs when sending the request from the server machine itself:
curl "http://localhost:9001/socket.io/?EIO=4&transport=polling"
I'm trying to create a socket.io server following the documentation.
I have the NodeJS socket server:
var http = require('http');
var socketio = require('socket.io');
var httpServer = http.createServer(utils.httpHandler);
httpServer.listen(config.socketio.port, function() {
console.log('The NodeJS HTTP server [port: ' + config.socketio.port + '] is listening...');
});
Using the DEBUG variable to start the server as in:
DEBUG=socket* node /usr/local/learnintouch/engine/api/js/socket/elearning-server.js 2>&1 >> /usr/local/learnintouch/logs/nodejs.log
shows:
socket.io:server creating engine.io instance with opts {"cors":{"origin":"*"},"path":"/socket.io"} +2ms
socket.io:server attaching client serving req handler +5ms
socket.io:server initializing namespace / +1ms
socket.io:server initializing namespace /elearning +10ms
The NodeJS log shows:
The NodeJS HTTP server [port: 9001] is listening...
The server object is:
{
io: Server {
_events: [Object: null prototype] {},
_eventsCount: 0,
_maxListeners: undefined,
_nsps: Map { '/' => [Namespace] },
parentNsps: Map {},
_path: '/socket.io',
clientPathRegex: /^\/socket\.io\/socket\.io(\.min|\.msgpack\.min)?\.js(\.map)?$/,
_connectTimeout: 45000,
_serveClient: true,
_parser: {
protocol: 5,
PacketType: [Object],
Encoder: [Function: Encoder],
Decoder: [Function: Decoder]
},
encoder: Encoder {},
_adapter: [Function],
sockets: Namespace {
_events: [Object: null prototype] {},
_eventsCount: 0,
_maxListeners: undefined,
sockets: Map {},
_fns: [Array],
_ids: 0,
server: [Circular],
name: '/',
adapter: [RedisAdapter],
[Symbol(kCapture)]: false
},
opts: { cors: [Object] },
[Symbol(kCapture)]: false
}
}
The connection is then handled like this:
module.exports.io = socketio(httpsServer, {
cors: {
origin: '*',
}
});
module.exports.io.adapter(ioredis({ host: config.redis.hostname, port: config.redis.port }));
var redisClient = redis.createClient(config.redis.port, config.redis.hostname);
module.exports.io.use(function (socket, handler) {
console.log('The namespace middleware is registered');
console.log(socket.request.headers.cookie);
if (socket.request.headers.cookie) {
socket.request.cookies = cookie.parse(decodeURIComponent(socket.request.headers.cookie));
socket.request.sessionID = socket.request.cookies['PHPSESSID'];
socket.request.socketSessionId = socket.request.cookies['socketSessionId'];
console.log("Authorization attempt with sessionID: " + socket.request.sessionID + " and socketSessionId: " + socket.request.socketSessionId);
redisClient.get("PHPREDIS_SESSION:" + socket.request.sessionID, function (error, reply) {
if (error) {
console.log("The redis client had an error: " + error);
return handler(new Error('The connection was refused because the redis client had an error.'));
} else if (!reply) {
console.log('The connection was refused because the redis client did not find the sessionID.');
return handler(new Error('The connection was refused because the redis client did not find the sessionID.'));
} else {
var redisSocketSessionId = utils.getRedisValue(reply, "socketSessionId");
if ('undefined' == typeof socket.request.socketSessionId || redisSocketSessionId != socket.request.socketSessionId) {
console.log('The connection was refused because the socketSessionId was invalid.');
return handler(new Error('The connection was refused because the socketSessionId was invalid.'));
} else {
console.log('The connection was granted.');
handler();
}
}
});
} else {
console.log('The connection was refused because no cookie was transmitted.');
return handler(new Error('The connection was refused because no cookie was transmitted.'));
}
});
The client connection:
<script type="text/javascript">
var elearningSocket;
$(function() {
if ('undefined' != typeof io && 'undefined' == typeof elearningSocket) {
console.log("Creating a socket on //dev.learnintouch.com:9001/elearning");
elearningSocket = io.connect('//dev.learnintouch.com:9001/elearning', { reconnect: true, rejectUnauthorized: false });
}
if ('undefined' != typeof elearningSocket) {
console.log("A socket on //dev.learnintouch.com:9001/elearning has been created");
elearningSocket.on('connect', function() {
console.log("The elearning namespace socket connected");
elearningSocket.emit('watchLiveCopilot', {'elearningSubscriptionId': '63', 'elearningClassId': '7'});
});
elearningSocket.on('postLogin', function(data) {
isAdmin = data.admin;
});
elearningSocket.on('message', function(message) {
console.log(message);
});
}
});
</script>
And the Chrome browser console:
Creating a socket on //dev.learnintouch.com:9001/elearning
A socket on //dev.learnintouch.com:9001/elearning has been created
But when sending a client connection, the log never shows the The namespace middleware is registered message.
Versions:
http#0.0.1-security
https#1.0.0
socket.io#4.1.3
cors#2.8.5
redis#3.1.2
socket.io-redis#6.1.1
connect#3.7.0
cookie#0.4.1
lodash#4.17.21
It looks like the connection cannot be established.
After a while the browser console shows an ERR_EMPTY_RESPONSE message as in:
socket.io.min.js:6 GET http://dev.learnintouch.com:9001/socket.io/?EIO=4&transport=polling&t=NbGNn6V net::ERR_EMPTY_RESPONSE
But the NodeJS socket server seems to be listening:
netstat -l | grep 9001
tcp6 0 0 [::]:9001 [::]:* LISTEN
The NodeJS socket server is not reachable.
But the firewall seems not to be the issue:
sudo ufw status verbose
Status: active
To Action From
-- ------ ----
9001 ALLOW IN Anywhere
The error can be seen live at
http://www.europasprak.com/elearning/subscription/2938/course
by first logging at
http://www.europasprak.com/engine/modules/user/login.php
with using the user demo#demo.com with the demo password.
UPDATE: I could solve the issue. It related to a handler preventing the connection from being established.
When changing the following:
module.exports.io.use((socket, handler) => {
to the following:
module.exports.io.of('/elearning').use((socket, handler) => {
the connection could then be done.

Answer 1

you need to determine whether the socket.io connection is successful, and then add events such as cores, adapters, events etc...to track down the problem step by step.
judging from the error report you provided above, socket.io was not established successfully.