Method drop

Source Code/20-01.rs:16–18

(&mut self)

    }
    impl Drop for CommunicationChannel {
        fn drop(&mut self) {
            println!("Closing port {}:{}", self.address, self.port);
        }
    }
    impl CommunicationChannel {
        fn create(address: &str, port: u16) -> CommunicationChannel {