1. A system for providing a messaging application program interface (API) for use in a computing environment, comprising: a computing appliance comprising one or more processor nodes, and a sender and a receiver executing thereon that support one or more application environments; a communication fabric connecting the one or more processor nodes and the application environments executing thereon; and a message bus implementation and messaging API that enables messaging within the computing appliance utilizing the communication fabric, wherein the message bus implementation surfaces inbound messages through the use of callbacks that enable a receiving application to be made aware of any inbound message data on a thread, including receiving, via the messaging API, a request from a sender's application environment to communicate message data to a receiver's application environment, storing the message data at a memory space location at the sender, communicating a notification to the receiver providing the location of the message data in the sender's memory space, the communicating including executing a send operation at the sender that initiates a write operation and an allocation of memory space at the receiver, requesting by the receiver that the message data be retrieved from its location at the sender, by initiating a read operation at the receiver to copy the message data to the receiver's memory space, and acknowledging, to the sender's application environment, receipt of the message data being transferred from the sender to the receiver, asynchronously with providing the message data to the receiver's application environment.