createOffer() function is returning incomplete sdp

Hi,

Im using this function for createOffer but its produces an incomplete sdp. Is there any idea?

peer.createOffer().then(desc => {
console.log(desc);
peer.setLocalDescription(desc).then(() => {
//socket.invoke(“offer”, id, JSON.stringify(peer.localDescription));
});
});

v=0 ↵o=- 7968195522823789820 2 IN IP4 127.0.0.1 ↵s=- ↵t=0 0 ↵a=msid-semantic: WMS ↵

Sorry i should have to call addStream function before creating an offer.