index.js

//public/index.js
...

var answersFrom = {}, offer;

socket.on('answer-made', function (data) {
    pc.setRemoteDescription(new sessionDescription(data.answer), function () {
        document.getElementById(data.socket).setAttribute('class', 'active');
        if (!answersFrom[data.socket]) {
            createOffer(data.socket);
            answersFrom[data.socket] = true;
        }
    }, error);
});