old_contents: //var Teachers = require('../models/teachers');
  //var TeacherClasses = require('../models/Teacher_classes');
  //var Classes = require('../models/classes');
  //var ClassLessons = require('../models/class_lessons');
  //var Lessons = require('../models/lessons');
  //var RequestedResponses = require('../models/requested_responses');
  
  module.exports = {
    getClasses: function(req, res, next) {
      var teacherId = req.body.teacherId;
  
      //TODO: get all classes through TeacherClasses
      //TeacherClasses.getAllClasses(teacherId);
    },
  
    getLessons: function(req, res, next) {
      //get all lessons based on req.body.classId
      var classId = req.params.classId;
  
      ClassLessons.hasMany(Lessons, {foreignKey: 'lessonId'})
      Lessons.belongsTo(ClassLessons, {foreignKey: 'lessonId'})
  
      var allLessons = Lessons.find({ where: {
        classId: classId,
      }, include: [ClassLessons]});
  
      return allLessons;
    },
  
    getPolls: function(req, res, next) {
      var lessonId = req.params.lessonId;
      // TODO: Query DB to list all the polls based on one single lesson ID
    },
  
    newPoll: function(req, res, next) {
      // TODO: post new poll to the db with the following object sent over: {lessonId, poll type}
      // then, after successfully posted to the DB, open up a socket event with a DB-generated
      // responseId and the poll type for students to send info back.
    },
  
    pollClass: function(io, req, res, next) {
      // var teacherId = req.body.teacherId;
      // var poll = req.body.poll;
  
      // this fake poll would normally be sent by the client to the socket, to the students' clients
      var poll = {
        responseId: 1,
        type: 'thumbs',
        datetime: new Date(),
        lessonId: 13,
      };
  
      io.on('connection', function(teacher){
  
        // FRONTEND-LISTENER: student.on('teacherConnect', () => {display('class is in session');});
        io.sockets.emit('teacherConnect');
          
        teacher.on('studentStandby', function(data) {
          // FRONTEND-LISTENER: teacher.on('newStudentConnected', (studentInfo) => {display(studentCount++ and studentInfo);});
          teacher.emit('newStudentConnected', data);
        });
  
  
        setTimeout(function(){
          io.sockets.emit('newPoll', poll);
        }, 5000);
  
        teacher.on('responseFromStudent', function(data) {
          // write data to the DB
          // TODO: DB query writing data
  
          // display data on frontend
          // FRONTEND-LISTENER: teacher.on('studentData', (data) => {display(data)});
          teacher.emit('studentData', data);
        });
  
      });
  
    },
  
  };
new_contents: //var Teachers = require('../models/teachers');
  //var TeacherClasses = require('../models/Teacher_classes');
  //var Classes = require('../models/classes');
  //var ClassLessons = require('../models/class_lessons');
  //var Lessons = require('../models/lessons');
  //var RequestedResponses = require('../models/requested_responses');
  
  module.exports = {
    getClasses: function(req, res, next) {
      var teacherId = req.body.teacherId;
  
      //TODO: get all classes through TeacherClasses
      //TeacherClasses.getAllClasses(teacherId);
    },
  
    getLessons: function(req, res, next) {
      //get all lessons based on req.body.classId
      var classId = req.params.classId;
  
      ClassLessons.hasMany(Lessons, {foreignKey: 'lessonId'})
      Lessons.belongsTo(ClassLessons, {foreignKey: 'lessonId'})
  
      var allLessons = Lessons.find({ where: {
        classId: classId,
      }, include: [ClassLessons]});
  
      return allLessons;
    },
  
    getPolls: function(req, res, next) {
      var lessonId = req.params.lessonId;
      // TODO: Query DB to list all the polls based on one single lesson ID
    },
  
    newPoll: function(req, res, next) {
      // TODO: post new poll to the db with the following object sent over: {lessonId, poll type}
      // then, after successfully posted to the DB, open up a socket event with a DB-generated
      // responseId and the poll type for students to send info back.
    },
  
    pollClass: function(io, req, res, next) {
      // var teacherId = req.body.teacherId;
      // var poll = req.body.poll;
  
      // this fake poll would normally be sent by the client to the socket, to the students' clients
      var poll = {
        responseId: 1,
        type: 'thumbs',
        datetime: new Date(),
        lessonId: 13,
      };
  
      io.on('connection', function(teacher){
  
        // FRONTEND-LISTENER: student.on('teacherConnect', () => {display('class is in session');});
        io.sockets.emit('teacherConnect');
          
        teacher.on('studentStandby', function(data) {
          // FRONTEND-LISTENER: teacher.on('newStudentConnected', (studentInfo) => {display(studentCount++ and studentInfo);});
          teacher.emit('newStudentConnected', data);
        });
  
  
        setTimeout(function(){
          io.sockets.emit('newPoll', poll);
        }, 5000);
  
        teacher.on('responseFromStudent', function(data) {
          // write data to the DB
          // TODO: DB query writing data
  
          // display data on frontend
          // FRONTEND-LISTENER: teacher.on('studentData', (data) => {display(data)});
          teacher.emit('studentData', data);
        });
        res.status(201).send('Hello from the teacher side');
      });
  
    },
  
  };
subject: Add response message