[Tradfri] Force session resume after communication errors (#4764)

As discussed in eclipse-archived/smarthome#6065 the tradfri gateway does not support a session resumption after a gateway reboot or other communcation errors.
Californium 1.0.7 is able to force a full handshake instead.
This change calls "forceResumeSessionFor" after a communication error, so that a full handshake is done.

Signed-off-by: Holger Reichert <mail@h0lger.de>

addons/binding/org.openhab.binding.tradfri/src/main/java/org/openhab/binding/tradfri/internal/handler/TradfriGatewayHandler.java

@@ -340,6 +340,14 @@ private synchronized void requestDeviceDetails(String instanceId) {
 
  @Override
  public void setStatus(ThingStatus status, ThingStatusDetail statusDetail) {
+ // to fix connection issues after a gateway reboot, a session resume is forced for the next command
+ if (status == ThingStatus.OFFLINE && statusDetail == ThingStatusDetail.COMMUNICATION_ERROR) {
+ logger.debug("Gateway communication error. Forcing session resume on next command.");
+ TradfriGatewayConfig configuration = getConfigAs(TradfriGatewayConfig.class);
+ InetSocketAddress peerAddress = new InetSocketAddress(configuration.host, configuration.port);
+ this.dtlsConnector.forceResumeSessionFor(peerAddress);
+ }
+
  // are we still connected at all?
  if (endPoint != null) {
  updateStatus(status, statusDetail);