Function serve 

pub async fn serve(
    listener: TcpListener,
    c2_enroll: SocketAddr,
    identity: Arc<NodeIdentity>,
    node_id: String,
    wake: Option<NodeWake>,
)

session.wake (handled here, never forwarded): {"token","nick","from","event_id","body"}, the letter event m4a’s M4A_LETTER_HOOK emits plus the node’s wake token.