Communication among devices in JSON message through MQTT
오전 7:41 Unknown 0 Comments Category :
This time, I made 3 layer which are device, gateway and server. The device publishes a JSON message to gateway, the server gets a message from gateway and sends a message to gateway, and the gateway gets message from both device and server and sends a message what device sent to server. This is a structure for this code.
pi 1 is a device, pi2 is a gateway and PC is a server as I said.
This is device(pi1) code:
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Device send JSON which has a device's name, sequence number and data(random number).
Gateway sends a message what it get from device and get a message from server. The server send a message that there was no problem.
This is device(pi1) code:
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var mqtt = require('mqtt');
var pi3_01 = mqtt.connect('mqtt://192.168.0.11');
var num = 0;
var count = 0;
var frequency = 5000;
function setPub(frequency)
{
setInterval(function() {
setNum();
count++;
console.log('frequency--->'+ frequency);
pi3_01.publish('pi3_02', JSON.stringify({From: 'pi3_02', seq: + count, data: +num}));
console.log('-------------------');
console.log(JSON.stringify({From: 'pi3_01', seq: + count, data: +num}));
}, frequency);
}
function setNum()
{
num = Math.floor(Math.random() *100) +1;
}
pi3_01.on('connect', function() {
console.log('pi3_01 on');
setPub(frequency);
});
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This is gateway(pi2) code:
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pi3_01.on('message', function(topic, message)
{
var jsontext = JSON.parse(message);
if(topic =='pi3_02')
{
PC.publish('pi3_01', JSON.stringify({seq: +jsontext.seq,
From: jsontext.From, data: +jsontext.data}));
console.log(jsontext);
}
if(topic =='PC')
console.log(jsontext)
});
function sub()
{
pi3_01.subscribe('pi3_02');
pi3_01.subscribe('PC');
}
function unsub()
{
pi3_01.unsubscribe('pi3_02');
pi3_01.unsubscribe('PC');
console.log('+++++++++++++++++++++++++++++++++++++++++');
}
loop();
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This gateway opens and closes subscribe frequently( every 5seconds ) so that gateway can save power when it closes subscribe.
This is server(PC) code:
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var mqtt = require('mqtt');
var PC = mqtt.connect('mqtt://192.168.0.15'); //PC Broker ip
var pi3_01 = mqtt.connect('mqtt://192.168.0.11'); //Gateway Broker ip
PC.subscribe('pi3_01');
PC.on('message', function(topic, message) {
var jsontext = JSON.parse(message);
console.log(jsontext);
pi3_01.publish('PC', JSON.stringify({From: 'PC', Message: 'I got it'}));
});
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The result is followed:
devices
Device send JSON which has a device's name, sequence number and data(random number).
Gateway
server
This server shows what it got from gateway and send a message to gate that it
So, there are 3 layers(device, gateway, and server) that communicate each other.
