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From: aperez@cvbnet.UUCP (Arturo Perez x6739)
Newsgroups: comp.unix.wizards
Subject: Re: buffer i/o using read(2) on BSD sockets
Message-ID: <85@cvbnetPrime.COM>
Date: 8 Mar 90 15:43:46 GMT
References: <637@lot.ACA.MCC.COM>
Sender: postnews@cvbnetPrime.COM
Lines: 29

From article <637@lot.ACA.MCC.COM>, by ables@lot.ACA.MCC.COM (King Ables):
> I've been using read(2) to read data from a socket and am having
> problems when the buffers get large.  I'm hoping someone has run
> into this before and knows what I am doing wrong.
> 
> I want to read an arbitrarily large block of data and not have to worry
> about message boundaries (hence read/write rather than send/recv).
> 
> 
> King Ables                    Micro Electronics and Computer Technology Corp.
> ables@mcc.com                 3500 W. Balcones Center Drive
> +1 512 338 3749               Austin, TX  78759

This is one of my pet peeves about BSD sockets.  There is no way
to read an arbitrary amount of data from a socket.  You have to be
aware of the kernel level buffering NO MATTER WHAT LEVEL your writing
your code at; i.e. apps, system, etc.

Why can't the kernel block your process until you get all the data you're
asking for (unless, of course, FIONBIO or O_NDELAY is set)?  If I'm
willing to wait, I'm willing to wait.  And if the connection goes down during
the transfer, I can live with that, too, just return an error.

Why was such a silly decision made?

Arturo Perez
ComputerVision, a division of Prime
aperez@cvbnet.prime.com
Too much information, like a bullet through my brain -- The Police