}
    } else {
      // The server reads the CONNECTION_PREFACE byte string.
      val connectionPreface = source.readByteString(CONNECTION_PREFACE.size.toLong())
      if (logger.isLoggable(FINE)) logger.fine(format("<< CONNECTION ${connectionPreface.hex()}"))
      if (CONNECTION_PREFACE != connectionPreface) {
        throw IOException("Expected a connection header but was ${connectionPreface.utf8()}")
      }