Connect working only if run code from Node repl

[pavel-karpovich]

You want to:

• report a bug
• request a feature

Current behaviour

The client does not connect to the server if the code is run from a file, and connects if you run the same code from the repl.

Steps to reproduce (if the current behaviour is a bug)

Code for Server:

const http = require("http");
const express = require("express");
const socketIO = require("socket.io");
const app = express();
const server = http.Server(app);
const io = socketIO(server);
io.on("connection", function(socket) {
    console.log("Wow! Client socket connected!");
});
server.listen(8081, "0.0.0.0", function() {
    console.log("Starting server on port 8081");
});

Code for Client:

const socketIOClient = require("socket.io-client");
const socket = socketIOClient("http://0.0.0.0:8081");
while (true);

Expected behaviour

Of course, I expect it to work correctly in both scenarios.

Setup

• OS: Windows 10 1809 and Amazon Linux AMI
• browser: without
• socket.io version: 2.2.0,

Other information (e.g. stacktraces, related issues, suggestions how to fix)

I am confused with this behavior...

Here is the trace of the SocketIO object. The first is when try run node client. The readyState becomes opening, connected false and disconnected true.

Socket {
io:
Manager {
    nsps: { '/sandbox': [Circular] },
    subs: [ [Object], [Object], [Object] ],
    opts:
    { path: '/socket.io',
        hostname: '0.0.0.0',
        secure: false,
        port: '8081' },
    _reconnection: true,
    _reconnectionAttempts: Infinity,
    _reconnectionDelay: 1000,
    _reconnectionDelayMax: 5000,
    _randomizationFactor: 0.5,
    backoff:
    Backoff { ms: 1000, max: 5000, factor: 2, jitter: 0.5, attempts: 0 },
    _timeout: 20000,
    readyState: 'opening',
    uri: 'http://0.0.0.0:8081/sandbox',
    connecting: [ [Circular] ],
    lastPing: null,
    encoding: false,
    packetBuffer: [],
    encoder: Encoder {},
    decoder: Decoder { reconstructor: null },
    autoConnect: true,
    engine:
    Socket {
        secure: false,
        agent: false,
        hostname: '0.0.0.0',
        port: '8081',
        query: {},
        upgrade: true,
        path: '/socket.io/',
        forceJSONP: false,
        jsonp: true,
        forceBase64: false,
        enablesXDR: false,
        timestampParam: 't',
        timestampRequests: undefined,
        transports: [Array],
        transportOptions: {},
        readyState: 'opening',
        writeBuffer: [],
        prevBufferLen: 0,
        policyPort: 843,
        rememberUpgrade: false,
        binaryType: null,
        onlyBinaryUpgrades: undefined,
        perMessageDeflate: [Object],
        pfx: null,
        key: null,
        passphrase: null,
        cert: null,
        ca: null,
        ciphers: null,
        rejectUnauthorized: true,
        forceNode: false,
        isReactNative: false,
        id: null,
        upgrades: null,
        pingInterval: null,
        pingTimeout: null,
        pingIntervalTimer: null,
        pingTimeoutTimer: null,
        transport: [XHR],
        _callbacks: [Object] },
    skipReconnect: false,
    _callbacks: { '$open': [Array], '$packet': [Array], '$close': [Array] } },
nsp: '/sandbox',
json: [Circular],
ids: 0,
acks: {},
receiveBuffer: [],
sendBuffer: [],
connected: false,
disconnected: true,
flags: {},
subs:
[ { destroy: [Function: destroy] },
    { destroy: [Function: destroy] },
    { destroy: [Function: destroy] } ],
_callbacks:
{ '$connecting': [ [Function: onConnecting] ],
    '$connect': [ [Function] ] } }

And second output, when you first run a node repl with node command. And then paste the same code to execute and all works:

Socket {
io:
Manager {
    nsps: { '/sandbox': [Circular] },
    subs:
    [ [Object], [Object], [Object], [Object], [Object], [Object] ],
    opts:
    { path: '/socket.io',
        hostname: '0.0.0.0',
        secure: false,
        port: '8081' },
    _reconnection: true,
    _reconnectionAttempts: Infinity,
    _reconnectionDelay: 1000,
    _reconnectionDelayMax: 5000,
    _randomizationFactor: 0.5,
    backoff:
    Backoff { ms: 1000, max: 5000, factor: 2, jitter: 0.5, attempts: 0 },
    _timeout: 20000,
    readyState: 'open',
    uri: 'http://0.0.0.0:8081/sandbox',
    connecting: [ [Circular] ],
    lastPing: null,
    encoding: false,
    packetBuffer: [],
    encoder: Encoder {},
    decoder: Decoder { reconstructor: null, _callbacks: [Object] },
    autoConnect: true,
    engine:
    Socket {
        secure: false,
        agent: false,
        hostname: '0.0.0.0',
        port: '8081',
        query: {},
        upgrade: true,
        path: '/socket.io/',
        forceJSONP: false,
        jsonp: true,
        forceBase64: false,
        enablesXDR: false,
        timestampParam: 't',
        timestampRequests: undefined,
        transports: [Array],
        transportOptions: {},
        readyState: 'open',
        writeBuffer: [],
        prevBufferLen: 0,
        policyPort: 843,
        rememberUpgrade: false,
        binaryType: null,
        onlyBinaryUpgrades: undefined,
        perMessageDeflate: [Object],
        pfx: null,
        key: null,
        passphrase: null,
        cert: null,
        ca: null,
        ciphers: null,
        rejectUnauthorized: true,
        forceNode: false,
        isReactNative: false,
        id: 'yKzSX2994gDxQs49AAAE',
        upgrades: [Array],
        pingInterval: 25000,
        pingTimeout: 5000,
        pingIntervalTimer:
        Timeout {
        _called: false,
        _idleTimeout: 25000,
        _idlePrev: [TimersList],
        _idleNext: [TimersList],
        _idleStart: 59120,
        _onTimeout: [Function],
        _timerArgs: undefined,
        _repeat: null,
        _destroyed: false,
        domain: [Domain],
        [Symbol(unrefed)]: false,
        [Symbol(asyncId)]: 615,
        [Symbol(triggerId)]: 604 },
        pingTimeoutTimer:
        Timeout {
        _called: false,
        _idleTimeout: 30000,
        _idlePrev: [TimersList],
        _idleNext: [TimersList],
        _idleStart: 59299,
        _onTimeout: [Function],
        _timerArgs: undefined,
        _repeat: null,
        _destroyed: false,
        domain: [Domain],
        [Symbol(unrefed)]: false,
        [Symbol(asyncId)]: 684,
        [Symbol(triggerId)]: 679 },
        transport: [WS],
        _callbacks: [Object],
        upgrading: false },
    skipReconnect: false,
    _callbacks: { '$open': [Array], '$packet': [Array], '$close': [Array] } },
nsp: '/sandbox',
json: [Circular],
ids: 0,
acks: {},
receiveBuffer: [],
sendBuffer: [],
connected: true,
disconnected: false,
flags: {},
subs:
[ { destroy: [Function: destroy] },
    { destroy: [Function: destroy] },
    { destroy: [Function: destroy] } ],
_callbacks:
{ '$connecting': [ [Function: onConnecting] ],
    '$connect': [ [Function] ] },
id: '/sandbox#yKzSX2994gDxQs49AAAE' }

[pavel-karpovich]

I figured it out...
This is because of my infinite loop and poor understanding of the js runtime ...
I thought the script should complete when the execution reached the end of the file, and wrote a loop to prevent this, but it seems instead I blocked the JS event loop.

Without loop all works fine. Sorry for trouble. :X