I am trying to transmit sensor data from an IoT device via CoAP using node-coap. The order of the data, as it arrives to the CoAP server, is important to me. I can not find a way to preserve the sequence of data, even when using the confirmable
request option.
I have a small program below that shows what I mean.
Can CoAP not be used if order/sequence of data is important? If it can, what am I doing wrong?
'use strict';
const coap = require('coap'),
cbor = require('cbor'),
server = coap.createServer();
const sequentialData = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
let incomingData = [];
let numResponses = sequentialData.length;
server.on('request', (req, res) => {
const obj = cbor.decodeFirstSync(req.payload);
incomingData.push(obj.data);
res.end();
});
server.listen(() => {
const reqOpts = {
hostname: 'localhost',
method: 'POST',
pathname: '/sequential',
options: {
Accept: 'application/cbor'
}
};
sequentialData.forEach((item) => {
const req = coap.request(reqOpts);
req.write(cbor.encode({
data: item
}));
req
.on('response', (res) => {
res.pipe(process.stdout);
res.on('end', () => {
if (--numResponses === 0) {
console.log(`got data in this order`, incomingData);
process.exit();
}
})
});
req.end();
});
});
Node Program above will output a different order each time ran.
via rynop
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