        3. *Must* contain at least one ASCII letter
        4. *Must* not begin or end with a hyphen
        5. Hyphens must not be adjacent to other hyphens
+
        For more details, see [RFC6335](https://tools.ietf.org/html/rfc6335#section-5.1).
 
      - receivedInvitation:

  // MARK: - Internal state

  /**
   Bool flag indicates if `Advertiser object` is advertising.
   */
  internal private(set) var advertising: Bool = false


  // MARK: - Private state

  /**
   MCNearbyServiceAdvertiser object.
   */
  private let advertiser: MCNearbyServiceAdvertiser

