Why doesn't PnPeer have to create answer and call setRemoteDescription?

[hieppq]

Hi` @GleasonK,

I'm new at webrtc

I've read your source code and dont understand this snippet code in class PnPeerConnectionClient:

private class CreateAnswerAction implements PnAction{
public static final String TRIGGER = "offer";
public void execute(String peerId, JSONObject payload) throws JSONException {
Log.d("CAAction","CreateAnswerAction");
PnPeer peer = peers.get(peerId);
peer.setType(PnPeer.TYPE_OFFER);
peer.setStatus(PnPeer.STATUS_CONNECTED);
SessionDescription sdp = new SessionDescription(
SessionDescription.Type.fromCanonicalForm(payload.getString("type")),
payload.getString("sdp")
);
peer.pc.setRemoteDescription(peer, sdp);
peer.pc.createAnswer(peer, signalingParams.pcConstraints);
}
}

private class SetRemoteSDPAction implements PnAction{
    public static final String TRIGGER = "answer";
    public void execute(String peerId, JSONObject payload) throws JSONException {
        Log.d("SRSAction","SetRemoteSDPAction");
        PnPeer peer = peers.get(peerId);
        SessionDescription sdp = new SessionDescription(
                SessionDescription.Type.fromCanonicalForm(payload.getString("type")),
                payload.getString("sdp")
        );
        peer.pc.setRemoteDescription(peer, sdp);
    }
}`

It looks useless and isnt used anywhere else. As I understand, the recipient has to create an answer and call setRemoteDescription. So could you explain it please?

Thank in advance.