Delivery-Date: Mon Nov 17 20:27:36 2008
Message-Id: <200811180424.mAI4OFbK002023@bourbon.usc.edu>
To: cs551@merlot.usc.edu
Subject: Re: cs 551 question on tcp
Date: Mon, 17 Nov 2008 20:24:15 -0800
From: Bill Cheng <william@bourbon.usc.edu>

Someone wrote:

  > Suppose I have 2 messages queued up at my socket stream.  A is a store msg
  > that was flooded and B is something else, say a keepalive. In part 1 I would
  > receive the entire message before i begin to process it. But now i first
  > peek into the message to see if its a store by receiving the header first
  > and then write the data in to a file in chunks. Now if  the coin flip says
  > "no", there is no point in reading and writing to a file as it will be
  > deleted later on. So is there anyway to delete part of message A from the
  > socket buffer without hurting the next message B. Like the next "datalen of
  > A" bytes from the socket stream, so that the next recv() call will start
  > reading from msg B.

TCP's stream of bytes abstraction does not allow you to do it!
Since it's a stream of bytes, there is no concept of a message
boundary.

This is a problem with the protocol design of the SERVANT
network.  If it is going to be a real peer-to-peer network,
we need to fix this.  (Not a bad final exam question if we
were to have long essay questions!  But since we don't have
long essay questions, this will not be on the exam.)
--
Bill Cheng // bill.cheng@usc.edu <URL:http://merlot.usc.edu/william/usc/>