how to subscribe client and save the data to mongodb in node.js, mosca,mqtt

I have a remote device which is nothing but a sensor. it will continuously give me some number. Actually I am receiving those number in my node.js server, I do not want to publish those data.I want to subscribe my client.And want to print my topic and message after client subscribed. Here is my Node.js server and mqtt in c. Run both the file using node app.js andgcc main.c after ./a.out. someone please help me to solve this problem. file shown in below:

/app.js

'use strict';

//dependencies
var express          = require('express'),
    passport         = require('passport'),
    strategy         = require('passport-local').Strategy,
    mongoose         = require('mongoose'),
    mongodb          = require('mongodb'),
    bodyParser       = require('body-parser'),
    path             = require('path'),
    acl              = require('acl'),
    mosca            = require('mosca');   


exports.init = function(pp) {
    passport = pp;
    app = pp;
    return exports;
};

exports.root = function(req, res) {
    // Running
    res.send("Running");
  };


//create express app
var app         = express();
    app.appname ="watersensor_DB";

//config mongoose
  mongoose.Promise = global.Promise;
  app.db = mongoose.createConnection('localhost/'+app.appname);
  app.db.on('error', console.error.bind(console, 'mongoose connection error: '));
  app.db.once('open', function () {
    // Store All Data
  });

//config mongodb
  mongodb.connect("mongodb://localhost/"+app.appname, function(error, mdb) {
  app.acl=new acl(new acl.mongodbBackend(mdb, app.appname));
  });

//config data models
  require('./models')(app, mongoose);

//Serve Frontend
  app.use(express.static(path.join(__dirname, '/public/')));

//config Routes
  var router = express.Router();
  require('./routes')(app, router, passport);

//config express
  app.set('secret','thisshouldnotbeinplaintext');
  app.use(bodyParser.urlencoded({ extended: false }));
  app.use(bodyParser.json());
  app.use(passport.initialize());
  app.use(router);


//config mosca
var ascoltatore = {
  //using ascoltatore 
  type: 'mongo',
  url: 'mongodb://localhost:27017/mqtt',
  pubsubCollection: 'ascoltatori',
  mongo: {}
};

var settings = {
  port: 1883,
  backend: ascoltatore,
  persistence: {
    factory: mosca.persistence.Mongo,
    url: 'mongodb://localhost:27017/mqtt'
  }
};

var server = new mosca.Server(settings);

server.on('clientConnected', function(client) {
    console.log('client connected', client.id);
});

// fired when a message is received 
server.on('published', function(packet, client) {
  console.log('Published', packet.payload); 
});


server.on('ready', setup);

// fired when the mqtt server is ready 
function setup() {
  console.log('Mosca server is up and running');
}

//Port Listening
  app.listen(7000, function(){
    //Running
    console.log("Node.js Server Is Running On localhost:7000");
  });

/main.c

#include <stdio.h>

main()
{
  char buf[1024];
  int i;  
    //mosquitto_sub -t 'test/topic' -v
    //mosqui<to_pub -t 'test/topic' -m 'hello'
  for(i=0; ;i++) {
    //sprintf(buf, "mosquitto_pub -h 192.168.43.82 -p 1883 -t 'test' -m '%d'",i);
    sprintf(buf, "mosquitto_pub -t 'test' -m '%d'",i);
    printf("%s\n",buf);
    system(buf);
    sleep(1);
  }

}

via ronny