Node.js app fails to connect using socket.io-client

Question

Background

I have a Node.js server using socket.io that accepts connections from clients via HTTPS.

I know this server works as I am able to connect to it via browser.

Problem

The problem is that I can't create a node app to connect to this server as a client.

I am using the following code:

const io = require("socket.io-client");

const socket = io.connect("https://my.website.com:3002", { secure: true, reconnect: true });

socket.on("connect", function(){
    console.log("connected");
});

socket.on("disconnect", function(){
    console.log("disconnected");
});

socket.on("error", console.error);

The server registers no connections, and this app logs no errors. It would seem that I am connecting to the wrong server, but this same URL works just fine when I use a browser.

Research

I have searched github and the official docs for an answer. Even similar questions from stackoverflow seem to not work:

Question

What am I doing wrong ?

I have the exact same code on browser and it works. This is what I find hard to understand. — Flame_Phoenix, Dec 07 '17 at 13:40
I got an output adding: `socket.on("connect_error", function(e){ console.log("connect_error", e); });` and waiting 20 sec. Looks like the `error` event is not emited for all types of errors -.- — Roland Starke, Dec 07 '17 at 13:56
I think it might be important to mention specifically the use of `https` in the title, as I spent 2 days hunting for this solution — RozzA, Apr 08 '18 at 04:52

score 20 · Accepted Answer · edited Nov 01 '19 at 08:29

Answer

After realising, that not all errors feed into the "error" event ( special thanks to @RolandStarke ) I found that I was having a consistent XHR pool request:

{ Error: xhr poll error
    at XHR.Transport.onError (/Users/pedro/Workspace/backend-stresser/node_modules/engine.io-client/lib/transport.js:64:13)
    at Request.<anonymous> (/Users/pedro/Workspace/backend-stresser/node_modules/engine.io-client/lib/transports/polling-xhr.js:128:10)
    at Request.Emitter.emit (/Users/pedro/Workspace/backend-stresser/node_modules/component-emitter/index.js:133:20)
    at Request.onError (/Users/pedro/Workspace/backend-stresser/node_modules/engine.io-client/lib/transports/polling-xhr.js:310:8)
    at Timeout._onTimeout (/Users/pedro/Workspace/backend-stresser/node_modules/engine.io-client/lib/transports/polling-xhr.js:257:18)
    at ontimeout (timers.js:469:11)
    at tryOnTimeout (timers.js:304:5)
    at Timer.listOnTimeout (timers.js:264:5) type: 'TransportError', description: 503 }

Once I had this information, I made a quick search and found a solution to this issue, which seems to be a bug:

https://github.com/socketio/socket.io-client/issues/1097

The code I am now using is:

const socket = io.connect("https://my.website.com:3002", { secure: true, reconnection: true, rejectUnauthorized: false });

And it works as expected.

After 2 days of bashing my head against a wall, this answer saved my arse. NONE of the other examples/answers that I found show how to do it with `https` — RozzA, Apr 08 '18 at 04:47
@Flame_Phoenix I am getting Parse Error HPE_INVALID_CONSTANT any clue? — user269867, May 30 '19 at 22:35
For me the key is `rejectUnauthorized: false` because I'm using a self signed certificate. — user5365075, Aug 27 '20 at 15:35

score 3 · Answer 2 · edited Apr 20 '21 at 12:45

3

I have used this code in my client side and it worked:

import io from "socket.io-client"
const SERVER = "http://localhost:5000"
const socket = io(SERVER, { transports: ["websocket"] })

edited Apr 20 '21 at 12:45

Adrian Mole

49,934
160
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answered Apr 20 '21 at 09:52

harshuuu 18

31
1

Adding transports parameters in socket constructor helped me a lot! Thanks! – Franciszek Job Aug 13 '21 at 08:57