01-05-2008
Processes Communication Only with flags!
hello everybody and a happy new year!
i am trying the client-server model...i have no problem with sockets etc...
especially for server:there is a father who is listening for TCP connections from clients,the later send commands which parent shares to his children.
then children execute commands and send the results to each client through UDP connectionless communication...
my problem is that father,who read commands from clients,read them to a pipe and children processes reads them from there...the first free child must read command from a pipe to which parent is writing.
unfortunately we are not supposed to use thread-mutex-shared memory-
we only can use a flag which allows a child to read o command (message from father each time) and i don't know how to use that flag...
i must have a flag to a pipe and the first free process takes the flag read the message and puts back the flag...how can i do something like that?
i see that there is a need for such a flag because when i have one pipe
and e.g.:5 children let the parent write a command to the pipe
then we need only one child to read the whole command...which won't happen without a flag preventing other children from reading until the above child reads the whole command and put back the flag...
thanks a lot!
note:we have NUMCHILDREN children given as an argument.
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LEARN ABOUT OSF1
xmdropsitequerystackingorder
XmDropSiteQueryStackingOrder(3X) XmDropSiteQueryStackingOrder(3X)
NAME
XmDropSiteQueryStackingOrder - A Drag and Drop function that returns the parent, a list of children, and the number of children for a spec-
ified widget
SYNOPSIS
#include <Xm/DragDrop.h>
Status XmDropSiteQueryStackingOrder (widget, parent_return, child_returns, num_child_returns)
Widget widget;
Widget *parent_return;
Widget **child_returns;
Cardinal *num_child_returns;
DESCRIPTION
XmDropSiteQueryStackingOrder obtains the parent, a list of children registered as drop sites, and the number of children registered as drop
sites for a given widget. The children are listed in current stacking order, from bottom-most (first child) to the top-most (last child).
This function allocates memory for the returned data that must be freed by calling XtFree. Specifies the widget ID. For this widget, you
obtain the list of its children, its parent, and the number of children. Returns the widget ID of the drop site parent of the specified
widget. Returns a pointer to the list of drop site children associated with the specified widget. Returns the number of drop site chil-
dren for the specified widget.
For a complete definition of DropSite and its associated resources, see XmDropSite(3X).
RETURN VALUE
Returns zero if the routine fails; returns a nonzero value if it succeeds.
SEE ALSO
XmDropSite(3X), XmDropSiteConfigureStackingOrder(3X)
XmDropSiteQueryStackingOrder(3X)