*
   * <p>Exceptions thrown by a listener will be propagated up to the executor. Any exception thrown
   * during {@code Executor.execute} (e.g., a {@code RejectedExecutionException} or an exception
   * thrown by {@linkplain MoreExecutors#directExecutor direct execution}) will be caught and
   * logged.
   *
   * <p>Note: If your listener is lightweight -- and will not cause stack overflow by completing

- 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.

- File Transfer Protocol (FTP) – Defined by RFC114 originally, and replaced by RFC765 and RFC959

There is a **special** environment variable called **`PATH`** that is used by the operating systems (Linux, macOS, Windows) to find programs to run.

The value of the variable `PATH` is a long string that is made of directories separated by a colon `:` on Linux and macOS, and by a semicolon `;` on Windows.

For example, the `PATH` environment variable could look like this:

//// tab | Linux, macOS

 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,

### [Routes](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-route/)

Routes supply the **dynamic** information necessary to actually connect to a webserver. This is the specific IP address to attempt (as discovered by a DNS query), the exact proxy server to use (if a [ProxySelector](https://developer.android.com/reference/java/net/ProxySelector.html) is in use), and which version of TLS to negotiate (for HTTPS connections).

 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,

 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,

 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,

 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,