3. Cascade Connect data transmission
Cascade Connect delivers data to an MS-Windows computer in the following way:
The method of data transmission between Cascade Connect and a QNX based client program is straight-forward synchronous communication. When a client sends a message to the Connect Server, it is blocked until it receives an acknowledgment that the message was received. The Connect Server then places the data message on the TCP/IP socket buffer (which acts like a queue) for delivery to Cascade Connect.
The size of a TCP/IP buffer is implementation-specific, and is typically 64K bytes. Once the message is passed to the TCP/IP buffer the Cascade Connect task is able to move on to processing the next data message. In this way, the communications between the Connect Server and Cascade Connect is asynchronous (by virtue of the TCP/IP buffer) up to the TCP/IP buffer size. If the data rate from the Connect Server to Cascade Connect exceeds the Windows task's ability to process it, then the TCP/IP buffer will fill, and the connection will become synchronous.
In order to guarantee an asynchronous connection, there must be an asynchronous mechanism in the QNX part of the data transmission path.