[homematic] Improve (re)connect handling to Homematic gateways (#11429)

* Use globally unique id for registration of callback to allow ...

the connection of multiple OH installations with one CCU.

The bridge id is not sufficient for this purpose because it is same in
all OH installations.


Signed-off-by: Martin Herbst <develop@mherbst.de>

* Retry callback re-registration after connection is resumed

Some services on the CCU need longer to start and are not available
immediately after the connection to the CCU has been resumed.

Improves the solution for #8808

Fixes #10439

Signed-off-by: Martin Herbst <develop@mherbst.de>

* Description was missing.

Signed-off-by: Martin Herbst <develop@mherbst.de>

* Changed setting name and description to avoid confusion


Signed-off-by: Martin Herbst <develop@mherbst.de>

* Added a troubleshooting tip to solve a communication problem


Signed-off-by: Martin Herbst <develop@mherbst.de>

* Shortened the label name to follow the guide lines

Signed-off-by: Martin Herbst <develop@mherbst.de>

* Print more information about the reason for the failure

Signed-off-by: Martin Herbst <develop@mherbst.de>

* Using scheduler thread pool and simplified configuration

Instead of configuring separate values for retry delays and number of
retries only the maximum time for retries can be configured.
The init method uses fixed delays.

Signed-off-by: Martin Herbst <develop@mherbst.de>

* Don't retry to send if gateway does not answer at all

Signed-off-by: Martin Herbst <develop@mherbst.de>

* Improved reconnect handling

- unregister callback not necessary if connection is lost
- wait 30s until clients and servers are restarted to give the gateway
some time to recover

Signed-off-by: Martin Herbst <develop@mherbst.de>

* Spotless

Signed-off-by: Martin Herbst <develop@mherbst.de>

* Cancel an active future if the binding is stopped

Signed-off-by: Martin Herbst <develop@mherbst.de>

bundles/org.openhab.binding.homematic/README.md

@@ -157,6 +157,13 @@ The port number of the HMIP server (default = 2010)
 - **cuxdPort**
 The port number of the CUxD daemon (default = 8701)
 
+- **groupPort**
+The port number of the Group daemon (default = 9292)
+
+- **callbackRegTimeout**
+Maximum time in seconds for callback registration in the Homematic gateway (default = 120s).
+For a CCU2, the value may need to be increased to 180s.
+
 - **installModeDuration**
 Time in seconds that the controller will be in install mode when a device discovery is initiated (default = 60)
 
@@ -676,6 +683,13 @@ Examples: HmIP-BROLL, HmIP-FROLL, HmIP-BBL, HmIP-FBL and HmIP-DRBLI4
 | openHAB | 0%   | 100%   |
 | CCU     | 100% | 0%     |
 
+** The binding does not receive any status changes from the Homematic gateway**
+
+First of all, make sure that none of the ports needed to receive status changes from the gateway are blocked by firewall settings.
+
+If the computer running openHAB has more than one IP address, a wrong one may have been set as receiver for status changes.
+In this case change the setting for `callbackHost` to the correct address.
+
 ### Debugging and Tracing
 
 If you want to see what's going on in the binding, switch the log level to DEBUG in the Karaf console