Asynchronous Network Communication

This section introduces asynchronous network communication, using sockets or Transport-Level Interface (TLI) for real-time applications. Asynchronous networking with sockets is done by setting an open socket, of type SOCK_STREAM, to asynchronous and non blocking. For more information on asynchronous sockets, see Advanced Socket Topics. Asynchronous network processing of TLI events is supported using a combination of STREAMS asynchronous features and the non-blocking mode of the TLI library routines.

For more information on the Transport-Level Interface, see Chapter 8, Programming With XTI and TLI.

Modes of Networking

Both sockets and transport-level interface provide two modes of service: connection-mode and connectionless-mode.

Connection-mode service is circuit-oriented. This service enables the transmission of data over an established connection in a reliable, sequenced manner. This service also provides an identification procedure that avoids the overhead of address resolution and transmission during the data transfer phase. This service is attractive for applications that require relatively long-lived, datastream-oriented interactions.

Connectionless-mode service is message-oriented and supports data transfer in self-contained units with no logical relationship required among multiple units. A single service request passes all the information required to deliver a unit of data from the sender to the transport provider. This service request includes the destination address and the data to be delivered. Connectionless-mode service is attractive for applications that involve short-term interactions that do not require guaranteed, in-sequence delivery of data. Connectionless transports are generally unreliable.