[Spread-users] prob. related to spread
jschultz at spreadconcepts.com
Fri Sep 8 11:00:05 EDT 2006
Currently, the spread library ultimately is potentially blocking in both
SP_receive and SP_*cast.
You can mitigate this issue to some extent by using select() on the
mailbox, which is a file descriptor, to test for incoming data and when
there is room to write on the socket. However, select() will signal that
the file descriptor is ready when there is *any* data to read, which can
cause SP_receive to block if more still has to come across the
client-daemon connection. Similarly, select() will signal write readiness
the first time a single byte can be written to the file descriptor without
You can further mitigate this problem by using either SP_poll or
ioctl(FIONREAD) to test the amount of data ready to be read in a
non-blocking manner and ioctl(FIONWRITE) (I think) to see how much can be
written in a non-blocking manner. On the read side, you have no way of
knowing how big the next message will be so you could still block but you
can at least wait until there is a significant amount of data. On the
write side, you should be able to wait until the file descriptor is open
enough to send your entire message and not block at all. The harder
question in those scenerios is how do you prevent your select() loop from
spinning because from select()'s POV the file descriptor is ready for
action. I don't have a good idea on that right this second. Maybe
someone else on the list can chime in with a good idea?
Phn: 443 838 2200
On Fri, 8 Sep 2006, Zahir Koradia wrote:
> Hi Pankaj,
> I am not very clear as to what you are looking for, but one thing that
> did understand from your mail was that you dont want to block on
> receive. There is function "SP_poll" which will allow you to poll your
> mailbox if there are any mails in it. This is a non blocking call. So
> once your "poll" says that you have something in you mailbox you can
> go ahead and receive it. That way your receive will not block since
> you know there is something waiting for you in the mailbox. I am not a
> frequent user of spread and so am not aware if the send also blocks.
> Logically speaking a send should not block.
> Hope this helps
> Zahir Koradia
> On 9/8/06, Pankaj Bhardwaj <pankajb83 at yahoo.co.in> wrote:
>> Hi Sir/Madam,
>> > I am having some prob. working with spread.
>> > I am using the spread server for communication.I have to develop
>> > client code which can send and receive data anytime.
>> > My probs.
>> > 1) I will be able to receive data and send that data
>> > 2) I will be able to create data and send that data.
>> > but these two things will be able to work simultaneously.
>> > like receive is a blocking call , if at that time i want to send data
>> > by creating myself i am able to do that.
>> > The prob i faced is that my program blocks in receive call. or in
>> > send.call
>> > until i do not send any data i am not able to receive any data.
>> > plz help us
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