Help (ipc question)

[Chris Torek]

> I am trying to write a program using 4.2 ipc stuff.  What I have
> discovered is that when the client does more than one send before
> the server does its recv (read), the server will receive both (all
> 70) messages at once [...].  I then have to go through the trouble
> of sep[a]rating these messages.  [...] Am I doing something wrong?
> Is ipc supposed to do this?

This is what's meant by ``byte stream'' or ``atomic'' protocols.  If
you have a stream protocol, it presents no record boundaries; if you
want any, you have to make them up yourself.  If you're using an
atomic protocol, then there is something inherent in the protocol
that makes each message a single unit.

TCP is a stream protocol.  UDP is a datagram (atomic) protocol.
However, UDP is not reliable (messages can [i.e., will] be dropped or
duplicated or reordered).  If you're working on a single machine you
can use AF_UNIX SOCK_DGRAM sockets to get a 99% reliable datagram
protocol.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251)
UUCP:	{seismo,allegra,brl-bmd}!umcp-cs!chris
CSNet:	chris at umcp-cs		ARPA:	chris at maryland