I am developing a node app using express which has a chatting system and I am using socket.io but I get this error

Server is listening on 3000

made socket connection

C:UsersUserMyFolderProjectsFMISappapp.js:139

socket.on('chat', function(data){

       ^



TypeError: socket.on is not a function

at Namespace.<anonymous> 

(C:UsersUserMyFolderProjectsFMISappapp.js:139:12)

at emitOne (events.js:116:13)

at Namespace.emit (events.js:211:7)

at Namespace.emit 

at _combinedTickCallback (internal/process/next_tick.js:131:7)

at process._tickCallback (internal/process/next_tick.js:180:9)

This what I have tried to do in my `app.js

var reload = require('reload');

var bodyParser =  require('body-parser');

var app = express();

var  socket = require('socket.io');

app.set('port', process.env.PORT || 3000);

app.set('view engine', 'ejs');

app.set('views','app/views');

app.locals.siteTitle = FMIS;

app.use(express.static('app/public'));



app.use(require('./routes/Chat_api'));

app.use(require('./routes/Chat'));



var server = app.listen(app.get('port'),()=>{

console.log('Server is listening on '+ app.get('port'));

});



var io = socket(server);



io.on('connection',function(){

    console.log('made socket connection');

    socket.on('chat', function(data){

        // io.sockets.emit('chat',data);

        console.log(data);

    });

});

reload(server, app);

I send and recieve data from the client like this

 socket.emit('chat',{

          user: chatUsername.value,

          Message: chatMessage.value

        });



socket.on('chat',function(data){

        // showMessage(data);

        console.log(data);

    });