Develop Reference

How to correctly call a function from Node.JS to Express.JS

I have a completed script that acts as a parser. The script is written in NodeJS and it works properly. The script returns an array of data and also saves it to my computer.
I would like to run this script from the frontend, at the click of a button. As far as I understand, I have to send a request to the server? It's suggested to use Express for the server, but I still haven't figured out how to call a third-party script from it, much less return any data from it.
Right now all I want is for my script to run when I make a request for the root directory "/" and send me a json in response (or for example a json file)
const express = require('express')
const runParser = require("./parser");
const app = express()
const port = 3000
app.get('/', async (req, res,next) => {
await runParser()
next()
})
app.listen(port, () => {
console.log(`Example app listening on port ${port}`)
})

All you need for Express is this:
const express = require('express');
const app = express();
const runParser = require("./parser");
const port = 3000;
app.get("/", (req, res) => {
runParser().then(results => {
res.json(results);
}).catch(err => {
console.log(err);
res.status(500).send("error");
});
});
app.listen(port, () => {
console.log(`Server running on port ${port}`);
});
And, then you can access that either by just going to:
http://localhost:3000
from your local host or
http://yourdomain.com:3000
in the browser or by issuing an ajax call to the desired URL from webpage Javascript.
I wouldn't personally put this type of activity on a GET request to / because that can be hit by things like web crawlers, search engines, etc...
It probably belongs on a POST (so crawlers won't issue it) and I'd personally put it on some pathname such as:
app.post("/runparser", (req, res) => {
// put your code here
});
And, then use a form submission or ajax call to that URL to trigger it.

Integrating socket.io with express is it a good idea? and if so how to go about it?

I'm must say I'm very new to back end development,
I'm currently working on an exercise project of making a fake money poker website. I use Node.js socket.io/express-session/passport
At first, I mainly used express with a HTTP server listening on one port. Averagely Like this:
const express = require("express")
const app = express()
app.get('/home',connectEnsureLogin.ensureLoggedIn("/loginPage"),function(req, res) {
//console.log(req.user.username+": sessionId: "+req.sessionID);
return res.sendFile( __dirname+"/website/index.html");
}
);
const PORT = process.env.PORT || 5000;
app.listen(PORT, () => console.log("Poker site Server started on ${PORT})")
The website wasn't working very fast. When a client joined a poker table they needed to ask the server every second for new updates on the state of the game so that was a lot of HTTP requests coming into my server. So I decided without much theoretical certitude that it seemed like a good idea: To have the server use socket.io sockets to hand info for clients that are in poker tables, but when they are not in poker tables and are just browsing the site I use a HTTP server to handle their request. Code wise I feel I haven't really managed to do this correctly. My code with Express, express-session, and passport combined makes sure only to hand information to users authenticated. But since The socket.io servers seem totally separate from all the express code, they don't share the same authentication functionality as the express code. So I need to somehow link my express and socket.io code so I can check if a client is authenticated before handing him any info via sockets. here is the system I'm currently using I didn't put all my code but I tried to summarize the essential parts:
const express = require('express');
const app = express();
//i creat the http server that is somehow linked with my express app when this server is listening
//it will call express handling methods.
const http = require('http').Server(app);
const io = require('socket.io')(http);
const path = require("path");
const passport = require("passport");
const connectEnsureLogin = require('connect-ensure-login');
const AccountInfo = require("./AccountInfo").AcccountInfo;
const expressSession = require('express-session')({
secret: process.env.SESSION_SECRET,
resave: false,
saveUninitialized: false
});
//passport setup
passport.use(AccountInfo.createStrategy());
passport.serializeUser(AccountInfo.serializeUser());
passport.deserializeUser(AccountInfo.deserializeUser());
//body parser
app.use(express.json());
app.use(express.urlencoded({ extended: true }));
//Sessions
app.use(expressSession);
//!!!!here is where I connect socket.io with the sessions i found this in another forum.
// thanks to this code I can access the session that a client is using when their socket connects.
io.use(function(socket, next) {
expressSession(socket.request, socket.request.res, next);
});
//so when a clients socket connects i save his socket.id to his session.
io.on('connection',function(socket) {
console.log(`socket.io connected: ${socket.id}`);
// save socket.io socket in the session
socket.request.session.socketio = socket.id;
socket.request.session.save();
});
//once the clients socket is connected directly after the clients sends a HTTP "PUT" request
//and this code answers it.
app.post('/Table/ConnectSocketToTable',Utilities.ensureLoggedIn(),function(req, res)
{
//I retrieve the socket using the socket.id I had saved in the session.
let socket = io.sockets.sockets.get(req.session.socketio);
let player = GetPlayerFromAnyTable(req.user.username);
if(player==null)//the player can't be in two tables at once
{
//since now we are in an express callback, express made sure that the client is indeed
//authenticated with the middle-ware: "Utilities.ensureLoggedIn()" also just before I made sure
//the client is not in another table. So we are good to go we can now link the socket to the table
//and have the client receive all the info about the state of his table
socket.join("table-"+req.session.passport.table);
req.user.socket = socket;
let table = GetTable(req.session.passport.table);
table.sitPlayer(req.user);
}
else
{
//the player is already connected so we just update his socket to a new one
player.requestUnseat=false;
player.account.socket =io.sockets.sockets.get(req.session.socketio);
}
socket.on('chatMessage', function(data,time) {
socket.to("table-"+req.session.passport.table).emit("chatMessage",req.user.username,data,time);
console.log(`send chat message : ${data}`);
});
socket.on('disconnect', function() {
GetTable(req.session.passport.table).requestUnsitUsername(req.user.username);
console.log(req.user.username +" was disconnected so now requesting unsit");
});
console.log("the socket of "+req.user.username+" has being connected to table-"+req.session.passport.table);
return res.sendStatus(200);
});
So for me, the way I'm doing this seems pretty bad since "app.post('/Table/ConnectSocketToTable'...)" and "io.on('connection',...)" are two different request listening functions I feel I should probably just do everything in one.
So should I do all the checks in the "io.on('connection',...)" function and somehow manage to make sure the client is authenticated within the callback of io.on('connection',callback) ?
or should I find a way to make the socket connection happen in the initial HTTP call the client uses to join a table, which is what I initially wanted?
But really I'm kinda lost because I'm telling myself maybe I don't even need Express anymore and I should just use socket.io for everything. I seem to clearly lack the general understanding that would allow me to know what approach I should be going for so any help is welcome. I started doing this self-made exercise to get into server-side development but also if there is any other recommended exercise to start up with back-end development I'm definitely interested in hearing about it.

From random testing I found out how to authenticate to my express session from the socket code you don't actually have to do it in the callback of io.on('connection',callback) you just need to add a few more middleware functions like this:
//connecting express sessions
io.use(function(socket, next) {
expressSession(socket.request, socket.request.res, next);
});
//connecting passport
io.use(function(socket, next) {
passport.initialize()(socket.request, socket.request.res, next);
});
//connecting passport sessions
io.use(function(socket, next) {
passport.session()(socket.request, socket.request.res, next);
});
//check if client is authenticated returns error if authentication failed
io.use((socket, next) => {
console.log("started socket Connection");
if(!socket.request.isAuthenticated&&socket.request.isAuthenticated())
{
socket.request.session.socketio = socket.id;
socket.request.session.save();
console.log("table "+socket.request.session.passport.table);
console.log("user.username "+socket.request.user.username);
console.log(`is authentificated`);
next();
}
else
{
console.log(`failed socket connection`);
next(new Error("unauthorized"));
}
});```

Express routing does not work with simple test case

I think I am missing some concept with basic routing for Express. See here
I created some simple test code as follows in my server index.js file.
app.get('/foo', function (req, res) {
console.log('foo path found');
res.send('foo achieved')
})
In my browser(chrome) URL I type
localhost:3000/foo
to trigger the route but I get no response on the server or client.
I verified localhost:3000 is up and running.
Port is set in a different file as follows:
app.set('port', (process.env.PORT || 3000));
But also I get confirmation in the terminal as follows:
const server = app.listen(app.get('port'), () => {
console.log('DEBUG: express: server up');
});
I am on a campus network that blocks some traffic, but b.c. this is localhost I don't think it should matter.

I don't think you're supplying enough information to correctly debug your issue.
I'd initially ensure that Express is listening on port 3000, double-check this line:
app.listen(3000);
Ideally, this line should be at the bottom of the script.
Response to edit: Yes, this should not matter. localhost is an alias for the system itself. It's a loopback, similar to that of 127.0.0.1.

It seems like you have created two express app, as you have mentioned that you are using two different files, the localhost which you are able to run is the one which has app.listen() code, but this doesn't have the app.get()
I suggest you use a single file for now and try doing it.
Try out the following code, and check now with localhost:3000/foo.
const express = require('express')
const app = express()
const port = 3000
app.get('/foo', function (req, res) {
console.log('foo path found');
res.send('foo achieved')
})
app.listen(port, () => console.log(`Example app listening at http://localhost:${port}`))

How to run multiple express servers on different ports?

Learning node from past week and got some hold on node and express. But now I am facing a problem. I am trying to run multiple express servers on different port and want them to return response after 10 seconds. After running the program, servers are starting fine but when I hit http://localhost:3000 or any of the server's url, observing following:
- on client side I am getting proper response from all servers after 10 secs
- server is getting into infinite loop and continuously printing "returning data..." after the delay of 10 secs
I tried using a function, using a js file to export the server and another class importing it and calling inside for loop. But sever is constantly printing "returning data..." after the delay of 10 secs. Below is my code:
var express = require('express');
const data = '{"key":"value"}';
const server = function (port) {
let app = express();
app.get('/', (req, res) => {
setInterval(function () {
console.log('returning data...')
res.end(data);
}, 10000); //want a delay of 10 secs before server sends a response
})
app.listen(port, () => console.log("Server listening at http://%s:%s",
"localhost", port))
}
console.log('\nStarting servers.......')
for (var i = 0; i < 5; i++) {
server(3000 + i)
}

You need to create multiple app instances from express. Below is the code snippet to start multiple server on different ports from same file.
var express = require('express');
let app1 = express();
let app2 = express();
app1.listen(3000, () => {
console.log("Started server on 3000");
});
app2.listen(3002, () => {
console.log("Started server on 3002");
});

You are using window.setInterval instead of window.setTimeout, that's why is running multiple times.

already answered: https://stackoverflow.com/a/71831233/17576982
(3 ways to start multiple servers on one run in nodejs)

Node.js on multiple domains using express.vhosts()

I'm back here with a nodejs problem, I am writing a node server that allows two or more app.js running on the same system using express.vhost(). But I'm quite lost now.
The webhost server is a dedicated server running Ubuntu and plesk and I've assigned 2 ip's for different domains.
xxx.xxx.xxx.123 IP is assigned to domain-one.com
xxx.xxx.xxx.xxx.456 is assigned to domain-two.com
both run a nodejs server app.js
and are each allocated in /var/www/vhosts/[domain-name]/node/app.js
The server running the vhost is at /var/www/node/server.js here is the code
var express = require("express");
var app = express();
app
.use(express.vhost('domain-one.com', require('/var/www/vhosts/domain-one.com/node/app.js').app))
.use(express.vhost('domain-two.com', require('/var/www/vhosts/domain-two.com/node/app.js').app))
.listen(3030);
app.get('/', function(req, res){
res.send('hello world the server running ');
});
While in each app.js
var express = require('express'),
routes = require('./routes');
var app = exports.app = express.createServer();
app.get('/', function(req, res){
res.send('hello world test file for [domain-name] running');
});
//port 3031 for domain-one.com
//port 3032 for domain-two.com
app.listen(3031);
then i run node server.js and every thing works fine without errors.
then i run a netstat -anltp
tcp 0 0 0.0.0.0:3030 0.0.0.0:* LISTEN 19839/node
tcp 0 0 0.0.0.0:3031 0.0.0.0:* LISTEN 19839/node
tcp 0 0 0.0.0.0:3032 0.0.0.0:* LISTEN 19839/node
Ok everything goes as i expected (i suppose) so i open my browser and type domain-one.com:3031 and in other tab domain-two.com:3032
but drops a Connection time-out in both domains... and when i run domain-one.com:3030 it displays the:
hello world the server running
But not in domain-two.com:3030 it hangs also..
I, want to get my head around this and understand a bit about how my server and domains work and how to manage to run diferent nodejs apps for diferent ip/domains in my server...
somethimes the domain-two.com prints what the domain-one.com app.js file res.send() supposed to print on the other domain...
I guess im very confused now... hope you can help me out with this..
Thanks a lot
-ivan

Perhaps better with this simple and precise syntax:
https://github.com/expressjs/vhost
//
// Module dependencies
//
var express = require('express');
var vhost = require('vhost');
var app = express();
//
// vhosts
//
app
.use(vhost('app1.io', require('./app1/app.js')))
.use(vhost('app2.io', require('./app2/app.js')))
.use(vhost('app3.io', require('./app3/app.js')))
.listen(8080);