DTJ Number 3 September 1987 - Digital Technical Journals

New ProductsIPROGRAMTOLOCALDIGITAL RECORD QUEUE ORCOMMANDMANAGEMENT 1/0LANGUAGE UTILITY SERVICES INTERFACE ! NETWORKDEVICEH1--HIGH-LEVELLANGUAGEHRUN TIMELIBRARYFigure 2All DECnet implementations provide task-totaskcommunication so that an application programcan exchange data with another programrunning on a remote system. In the VMS environment,task-to-task communication can be performedby the RMS services as if a file were beingaccessed. This capability is made possible by twodesign decisions.The first decision was to model task-to-taskcommunications within RMS as though it weresent to a bidirectional unit-record device. Thistype of device has many properties of a terminalor VMS mailbox. These properties allow an applicationprogram (or command procedure) toshare data with its remote counterpart throughsequential GET and PUT requests, just as if theprogram were processing a local data file. Furthermore,a CLOSE operation initiated by eitherpartner is signaled to the other as an end-of-filecondition.The second decision was to extend the syntaxof the quoted string form of an RMS file specificationwas extended to accommodate the identificationof a remote task, as described earlier.When the file specification passed to RMS onan OPEN request contains a quoted network taskspecifier, RMS will connect to the remote task orobject identified in the string instead of to theFAL object. The remote VMS process can thencomplete the connection by issuing an OPENrequest using the logical name SYS$NET. In subsequent1/0 requests from either cooperatingtask, data records are passed directly to and fro mthe remote task without using DAP, which isrequired when communicating with FAL.Interfa ce Levels fo r the VMS SystemIDECnet-VAX Building BlocksNetwork PrimitivesDECnet-VAX provides task-to-task communicationsbetween different nodes within a network.layered network applicati