Re: what is a reasonable socket select() wait time?

I've been using 15 seconds regularly and double it to 30 seconds for
satellite connections.

You should be running with either a block counter or a delimiter. The block
counter allows for encryption whereas the delimiter will not.

Ken Slaugh  (707) 795-1512 x118
Chouinard & Myhre, Inc.
AS/400 Professional Administrator/MSE
Client Access Specialist
http://www.cm-inc.com/



                    Rich Duzenbury
                    <rduz@westernmid        To:     mi400@midrange.com
                    range.com>              cc:
                    Sent by:                Subject:     Re: [MI400] what is a 
reasonable
                    mi400-admin@midr        socket select() wait time?
                    ange.com


                    04/22/2002 12:33
                    PM
                    Please respond
                    to mi400







>
>Why does the select() periodically fail?  How can my client truly, TRULY
>determine if more data is available from the server?  Do I need a non-zero
>wait time?  What is a reasonable value?

I don't think select is 'failing' per se.  There just isn't any data
-yet-.  Lost & retransmitted packets by the underlying transport mechanism
could cause this, as another poster mentioned.  A busy network might also
cause select give up before any data is available.

Perhaps I read too much into your message, but I wonder how your actual
protocol is setup.  The receive side of the socket knows how much data to
expect, right?

If you send a fixed length message, your read loop should loop until a
complete message is read, or an error occurs.

If you send a delimited message - e.g. a null byte at the end of each
message, your read loop should read until the null is located, or an error
occurs

Otherwise, you could preface a variable length message with the number of
bytes to follow, and then loop until that many bytes are received, or an
error occurs.

The point is, the receive loop has to *know* how much data to look for.
Also, the loop must be prepared to receive a message in 'chunks' or
'pieces' by comparing the received count with the requested count, and
acting accordingly by requesting to read the remaining data.

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