[HECnet] Sample DCL code for simple client-server task-to-task comms

On 2013-01-17 13:17, Brian Schenkenberger, VAXman- wrote: sampsa at mac.com writes: How come writing to SYS$NET doesn't send any output? FOOBAR.COM is now: $WRITE SYS$NET "Foobar" $DIRECTORY/OUTPUT=SYS$NET But I only get the directory listing. Before you can WRITE to any device, and SYS$NET is, in essence here, a device, you must first OPEN a channel to it. In DCL, the OPEN command will create the channel and assign the channel to a logical name which can subsequently be used in the WRITE. You cannot WRITE to a terminal or a file without OPENing a channel either, for example: $ SHOW LOGICAL TT "TT" = "_FTA207:" (LNM$PROCESS_TABLE) $ WRITE TT "Hello World!" %DCL-W-UNDFIL, file has not been opened by DCL - check logical name $ OPEN/WRITE MY_TERMINAL TT: $ WRITE MY_TERMINAL "Hello World!" Hello World! $ WRITE will always return with error if the channel has not first been OPENed. The /OUTPUT=SYS$NET tells the DIRECTORY command to send its output to SYS$NET. Internally, the DIRECTORY command issues an RMS $OPEN before it issues any RMS $PUT to output the directory's listing. The channel is implicitly $CLOSEd as part of image rundown. Your channel to SYS$NET, since you don't explicitly issue a DCL CLOSE, will be implicitly CLOSEd as a feature of process rundown. How does that work when several processes want to open the device? For example, in this case, if DCL opened SYS$NET, and then you run DIRECTORY with output directed to SYS$NET. Can DIRECTORY be allowed to open the device, even though DCL already have it open? Also, what happens at close. Is the connection terminated when SYS$NET is closed, or is the connection still around until the process is terminated? Can another open be done on the same SYS$NET, and you can continue exchanging data? Johnny