Connection status between Cloud and the Host Machine

Hi, communities

Please tell me about the connection status between "Appian RPA (Cloud)" and the Host Machine with "Appian RPA Agent" are installed.
When Appian Cloud instructs "RPA" processing from "Process", I think it's the flow of below,
    Cloud -----> Host Machine(Agent)
but how is this connection started in the first place?

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A) Just issue an order from the Cloud to the Host Machine
1. Session Start & RPA instructions
    Cloud -----> Host Machine(Agent)
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B) Agent initiates a session, and Cloud requests using that session
1. Session Start & stay connected
    Host Machine(Agent) -----> Cloud

2. RPA instructions
    Cloud -----> Host Machine(Agent)
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C) Other than those above