Node JS emit socket after error in SQL query - sql

Question

**Hello, please do you know how can I send message to client via socket when I have error in my SQl query on server side ? **
Server side
io.on('connect', (socket) => {
console.log("User connected: " + socket.id);
socket.on('disconnet', () => {
console.log("disconnected");
})
.post('/addDiel', (req, res) => { //Pridanie dielu do DB
pool.getConnection((err, connection) => {
if(err) throw err
console.log(`Pripojene ako ID ${connection.threadId}`)
const params = req.body;
res.send({
MenoDielures: params.MenoDielu,
DruhDielures: params.DruhDielu,
ProjektNameres: params.ProjektName
})
ProjektNameDB = params.ProjektName.split('.').join("_");
connection.query('INSERT INTO `Skener_db`.`?` (`MenoDielu`, `DruhDielu`, `DatumCas`) VALUES (?, ?, NOW())', [ProjektNameDB, params.MenoDielu, params.DruhDielu],(err, rows)=> {
connection.release()
if(!err) {
res.send(console.log(`Hodnota ${params.MenoDielu} bola pridana.`))
} else {
console.log(err);
if (err.code == ('ER_DUP_ENTRY')) {
//send message to client
}
//res.send({alertMessage: 'Diel už bol oskenovaný. Oskenuj ďaľší.'})
}
})
console.log(req.body)
})
})
})
My client side:
socket.on('connect', () => {
$('#skuska').html("Socket pripojeny");
})
socket.on('receiveDUPmessage', message => {
$('#skuska').html(message);
})
The code here is just for example. I didnt find solution for my problem, so I'm asking here

Answer 1

You have to emit events and socket is locally scoped. io.sockets is not, So you can do it like this on the server-side:
if(!err) {
res.send(console.log(`Hodnota ${params.MenoDielu} bola pridana.`))
} else {
console.log(err);
if (err.code == ('ER_DUP_ENTRY')) {
//send message to client
io.sockets.emit('my error', 'Some error happened');
}
//res.send({alertMessage: 'Diel už bol oskenovaný. Oskenuj ďaľší.'})
}
And on the client-side do this:
socket.on('my error', function (text) {
console.log(text);
});
Here is some sort of posts that may help you:
How to emit error to be possible catch it on error handler on client-side?
How to emit a socket.io response within post request in NodeJS