From owner-freebsd-hackers  Fri Nov 15 11:34:00 1996
Return-Path: owner-hackers
Received: (from root@localhost)
          by freefall.freebsd.org (8.7.5/8.7.3) id LAA10921
          for hackers-outgoing; Fri, 15 Nov 1996 11:34:00 -0800 (PST)
Received: from alpha.xerox.com (alpha.Xerox.COM [13.1.64.93])
          by freefall.freebsd.org (8.7.5/8.7.3) with SMTP id LAA10916
          for <hackers@freebsd.org>; Fri, 15 Nov 1996 11:33:53 -0800 (PST)
Received: from crevenia.parc.xerox.com ([13.2.116.11]) by alpha.xerox.com with SMTP id <16073(6)>; Fri, 15 Nov 1996 11:33:17 PST
Received: from localhost by crevenia.parc.xerox.com with SMTP id <177557>; Fri, 15 Nov 1996 11:33:05 -0800
To: Terry Lambert <terry@lambert.org>
cc: fenner@parc.xerox.com (Bill Fenner), scrappy@ki.net, jdp@polstra.com,
        hackers@freebsd.org
Subject: Re: Sockets question... 
In-reply-to: Your message of "Fri, 15 Nov 96 10:58:51 PST."
             <199611151858.LAA26626@phaeton.artisoft.com> 
Date: Fri, 15 Nov 1996 11:32:55 PST
From: Bill Fenner <fenner@parc.xerox.com>
Message-Id: <96Nov15.113305pst.177557@crevenia.parc.xerox.com>
Sender: owner-hackers@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

In message <199611151858.LAA26626@phaeton.artisoft.com> you write:
>So at the "read" interface, you *can* count on it arriving in the
>same sized chunks as you wrote it

No, you can *never* count on that, since non-blocking reads from a stream
socket return as much data as is available, which could be less than you
asked for.  See soo_read() (or soo_rw() in earlier BSD's) and soreceive().

4.4BSD introduced the MSG_WAITALL flag, so if you use recv() or any of its
friends you can ask for your whole request to be performed.  This is, of
course, not portable, and MSG_WAITALL won't even do the trick if your
request is larger than the socket's high water mark (e.g. SO_RECVBUF).

  Bill