*  2. Open a sink to write the request body. Either [known][newKnownLengthSink] or
 *     [chunked][newChunkedSink].
 *  3. Write to and then close that sink.
 *  4. [Read response headers][readResponseHeaders].
 *  5. Open a source to read the response body. Either [fixed-length][newFixedLengthSource],
 *     [chunked][newChunkedSource] or [unknown][newUnknownLengthSource].
 *  6. Read from and close that source.
 *

      tunnelCodec.writeRequest(nextRequest.headers, requestLine)
      tunnelCodec.finishRequest()
      val response =
        tunnelCodec.readResponseHeaders(false)!!
          .request(nextRequest)
          .build()
      tunnelCodec.skipConnectBody(response)

      when (response.code) {
        HttpURLConnection.HTTP_OK -> return null