The CubeSat created when sending is not used. There are inconsistencies with how the previous paragraphs build up the code. Listing 4.14 has the recipient CubeSat as an argument:

impl GroundStation {
    fn send(
      &self,
      mailbox: &mut Mailbox,
      to: &CubeSat,
      msg: Message,
    ) {
    // ...
  }
}”

In the final version (Listing 4.15) the argument is suddenly gone. As a result the base station no longer "needs to connect" to the satellite to send it a message.