|
FAST Protocol
< Previous Next >
Re: FAST over TCP
janaka Sooriyaarachchi / MillenniumIT <>
11 Jan 2010 6:17AM ETBut please see FAST 1x1: 10 - Transfer Encoding section. It say that it is not a optional field.
(FAST 1x1: 10 - Transfer Encoding - A block is a sequence of one or more messages. A block has a leading block size specifying the number of bytes occupied by the messages of the block. It is a dynamic error [ERR D12] if a block has zero size. The block size is represented as an Unsigned Integer which may be overlong. The overlong property is defined in the Integer Numbers section below)
> Thanks for your quick reply!
>
> > Hi,
> >
> > Frame length is a feature that must be agreed on bi-laterally. There
> > is nothing in the wire data that tells you it is there and it is
> > currently not used in any impl as far as I know.
> >
> > Frame length is optional and it was included in the std to simplify
> > parsing for those who wanted to build a more naive FAST decoder over
> > TCP. Depending on how you implement your decoder you may or may not
> > have use for a frame length. A side-effect of using the frame length
> > construct is that you can skip over a message that you don't
> > recognize.
> >
> > This is not without complications as you must make sure that the
> > previous value state for your field encoding operations remain intact.
> > So, even if you don't know how to decode the message you have to know
> > that there are no dependencies to messages that you do know and
> > therefore can parse.
> >
> > The rules and best practices around frame length are still somewhat
> > untested, so proceed with caution.
> >
> > I recommend that you don't use frame length unless you believe you
> > have a strong reason to use it.
> >
> > HTH, Rolf
> >
> > > Hi,
> > >
> > > I read http://www.fixprotocol.org/documents/2301/A%20Basic%20Guide%20to-
> > > %20FAST%20v1.0.pdf.
> > >
> > > I am confused about the frame length field mentioned on page 17.
> > >
> > > I am sending an encoded message over TCP (socket). So do I need to
> > > prefix the message with the length of the message?
> > >
> > > If yes, how does the receiver know that it is a new message (given
> > > that date transferred over TCP is just a byte stream)?
> > >
> > > If it has been asked, please give me a pointer. (A little bit hard
> > > to use the search function here...:()
> > >
> > > Thanks in advance!
Re: FAST over TCP
janaka Sooriyaarachchi / MillenniumIT 11 Jan 2010 6:17AM ET
|
