client.setURI(uri + "/obs").useCONs();
System.out.println("===============\nCO04");
System.out.println("---------------\nGET /obs with Observe");
CoapObserveRelation relation4 = client.observeAndWait(
new CoapHandler() {
@Override public void onLoad(CoapResponse response) {
String content = response.getResponseText();
System.out.println("-CO04----------");
System.out.println(content);