Await for function before end() - node.js

Question

edit: added a bit more code.
const express = require('express');
var bodyParser = require('body-parser');
const app = express();
var urlencodedParser = bodyParser.urlencoded({extended: false})
const {google} = require('googleapis');
const {PubSub} = require('#google-cloud/pubsub');
const iot = require('#google-cloud/iot');
const API_VERSION = 'v1';
const DISCOVERY_API = 'https://cloudiot.googleapis.com/$discovery/rest';
app.get('/', urlencodedParser, (req, res) => {
const projectId = req.query.proyecto;
const cloudRegion = req.query.region;
const registryId = req.query.registro;
const numSerie = req.query.numSerie;
const command = req.query.command;
const client = new iot.v1.DeviceManagerClient();
if (client === undefined) {
console.log('Did not instantiate client.');
} else {
console.log('Did instantiate client.');
sendCom();
}
async function sendCom() {
const formattedName = await client.devicePath(projectId, cloudRegion, registryId, numSerie)
const binaryData = Buffer.from(command);
const request = {
name: formattedName,
binaryData: binaryData,
};
return client.sendCommandToDevice(request).then(responses => res.status(200).send(JSON.stringify({
data: OK
}))).catch(err => res.status(404).send('Could not send command. Is the device connected?'));
}
});
const PORT = process.env.PORT || 8080;
app.listen(PORT, () => {
console.log(`App listening on port ${PORT}`);
console.log('Press Ctrl+C to quit.');
});
module.exports = app;
I have this function, that I call after the client initiate: sendCom();
async function sendCom() {
const formattedName = await client.devicePath(projectId, cloudRegion, registryId, deviceId)
const binaryData = Buffer.from(command);
const request = { name: formattedName, binaryData: binaryData, };
client.sendCommandToDevice(request)
.then(responses => {
res.status(200).send(JSON.stringify({ data: OK })).end();
})
.catch(err => {
res.status(404).send('Could not send command. Is the device connected?').end();
});
}
My problem is that sendCommandToDevice gets executed perfectly, however I get the catch error.
As I understand it, it's because in the .then ends the connection.
I've looked at this and thats's what I tried, however I'm not sure I understand what's going on.

Answer 1

You can not use send with end.
end() is used when you want to end the request and want to respond with no data.
send() is used to end the request and respond with some data.
You can found more about it here.