Send a message using the connection of the watch. If it cannot be sent
immediately, it will be queued for transmission in watch. The contents of
message will then be serialized and transmitted when the connection of the
watch becomes writable. In case the message is queued, the ID returned in
id will be non-zero and used as the ID argument in the message_sent
callback.
Send a message using the connection of the watch. If it cannot be sent immediately, it will be queued for transmission in watch. The contents of message will then be serialized and transmitted when the connection of the watch becomes writable. In case the message is queued, the ID returned in id will be non-zero and used as the ID argument in the message_sent callback.