Sends command to a running instance of this.
If you need to pass data to the instance, you should create a MessageData object using MessageData and then fill it with the data you intend to pass.
The running application will receive a UniqueApp:UniqueApp:message-received signal and will call the various signal handlers
attach to it. If any handler returns a Response different than
unique_response_ok, the emission will stop.
| this |
a App |
| command_id |
command to send |
| message_data |
MessageData, or null |
|
The Response returned by the running instance |