Can't get websocket client to run as child process - node.js

Question

I'm looking to build a project based on node that will have a few different websocket connections, I'm fine with the code itself for what I want to do but can't seem to get my head around how to start the websocket modules (code already written and moved to a file named ws.js) to run from the main server.js file.
I have tried spawning as a child process but just get
Error: spawn ws.js ENOENT
I have removed all other code from each file to prevent hidden errors, content of the files are below.
Server.js
var child = require('child_process').spawn('node', ['ws.js']);
child.stdout.on('data', function (data) {
console.log('stdout: ' + data);
});
child.stderr.on('data', function (data) {
console.log('stderr: ' + data);
});
child.on('exit', function (code) {
console.log('child process exited with code ' + code);
});
setTimeout(function() {
child.stdin.write('echo %PATH%');
}, 2000);
ws.js
const Gdax = require('gdax');
const publicClient = new Gdax.PublicClient();
const websocket = new Gdax.WebsocketClient(['BTC-USD', 'ETH-USD']);
websocket.on('message', data => {
/* work with data */
console.log("data received");
});
websocket.on('error', err => {
/* handle error */
});
websocket.on('close', () => {
/* ... */
});
EDIT --------------------------
Thanks for the response below from Elliot server.js now runs without error however the ws.js child never writes to the console so is either not running or failing silently. Any help is appreciated on getting this working.
Cheers

Answer 1

For the console logs, you have to keep in mind that a child process is a new process and does not share a console. You can make it work with spawn(), however, since you are using a child process to execute a nodeJs file, I recommend using child_process.fork() instead of spawn. It is similar to spawn but is specifically used for other nodeJs processes. The benefit is that it makes it much easier for the two processes to communicate.
With that in mind, you can make the following updates:
Server.js:
var child = require('child_process').fork('./ws.js');
child.on('message', function (data) {
console.log('stdout: ' + data);
});
child.on('error', function (data) {
console.log('stderr: ' + data);
});
child.on('exit', function (code) {
console.log('child process exited with code ' + code);
});
ws.js
const Gdax = require('gdax');
const publicClient = new Gdax.PublicClient();
const websocket = new Gdax.WebsocketClient(['BTC-USD', 'ETH-USD']);
websocket.on('message', data => {
/* work with data */
process.send("data received");
});
websocket.on('error', err => {
/* handle error */
});
websocket.on('close', () => {
/* ... */
});
process.send() sends data to its parent process, where a listener (i.e.
child.on('message', callback)) is waiting to receive it.