* callback has returned. Synchronous calls become idle once [execute()][Call.execute] returns.
   * This means that if you are doing synchronous calls the network layer will not truly be idle
   * until every returned [Response] has been closed.
   */
  var idleCallback: Runnable? = null
    get() = this.withLock { field }
    set(value) {
      this.withLock { field = value }
    }

* Designed around these standards, after a meticulous study. Instead of an afterthought layer on top.
* This also allows using automatic **client code generation** in many languages.

### Automatic docs

- Secure File Transfer Protocol (SFTP) – Defined by the Internet Engineering Task Force (IETF) as an
  extended version of SSH 2.0, allowing file transfer over SSH and for use with Transport Layer
  Security (TLS) and VPN applications.

- File Transfer Protocol over SSL/TLS (FTPS) – Encrypted FTP communication via TLS certificates.