The data included in each message depends on the type of message - bearing in mind that a single FXB.Message can contain multiple types of message.
For example, a PRICE message will contain a quotes[] array of new prices. An ORDER_OPEN message will contain an ordersOpened[] array of new orders. These extra properties are described below.
If a message is both a PRICE message and an ORDER_OPEN message, then it will contain bothquotes[] and ordersOpened[].
