Re: Sockets library requirements

From: davlet_panech (davlet_panech_at_[hidden])
Date: 2002-02-25 16:28:34

--- In boost_at_y..., "gtpaw" <gtpaw_at_w...> wrote:
> When implementing an interprocess communication (IPC) mechanism, the
> developer usually ends up with the same top-level design, no matter 
what is the underlying
> communication engine (sockets, shared memory, pipes, etc.). 
> Hence, IMHO, the socket library's functionality should be 
restricted to the following 
> primitive operations: connect, listen, send, recv. 

Yes, but what about connectionless protocols, like UDP? (accept() and 
listen() are meaningless for these). Do we want to support them? 
Obviusly limiting the socket library to TCP only will simplify 
everything. Another issue is that availability of protocols can 
frequently be determined at runtime only (although TCP is probably 
always supported). Yesterday I was playing around with my own socket 
library that supports UDP, only to discover that UDP isn't installed 
on my machine (NT4.0). That makes me wonder if compile-time protocol 
binding is a good idea.

> 
> Naturally, If we get the details right, we can also implement a
> corresponding pipe library, and a shared memory library. 
> 
> At the next step, we can create an IPC library, which will use 
either
> of the above-mentioned libraries. This library would support both 
blocking and non-blocking
> I/O operations, thru an inserter/extractor interface:
> 
> 
> typedef boost::ipc<boost::socket> my_ipc_t;
> my_ipc_t my_ipc;
> .
> .
> //  writer1 uses a 1000 ms timeout period
> my_ipc_t::writer_type writer1 = my_ipc.make_writer(1000); 

Doesn't this imply that a writer is copyable? I don't think it's a 
good idea.

> writer1 << "Hello there\n";
> .
> .
> //  writer2 is blocking
> my_ipc_t::writer_type writer2 = my_ipc.make_writer(); 
> writer2 << "Hello again\n";
> 

It's also unclear what socket streams would look like. How do the two 
connected sockets coordinate byte ordering, locales, etc.?

D.P.

> 
> Comments are highly appreciated
> -Itay