Re: [9fans] channels across machines

[Bakul Shah <bakul+plan9@bitblocks.com>]

On Sat, 18 Jul 2009 06:25:19 EDT erik quanstrom <quanstro@quanstro.net>  wrote:
> On Sat Jul 18 03:46:01 EDT 2009, bakul+plan9@bitblocks.com wrote:
> > Has anyone extended the idea of channels where the
> > sender/receiver are on different machines (or at least in
> > different processes)?  A netcat equivalent for channels!
>
> i think the general idea is that if you want to do this between
> arbitrary machines, you provide a 9p interface.  you can think
> of 9p as a channel with a predefined set of messages.  acme
> does this.  kernel devices do this.
>
> however inferno provides file2chan
> http://www.vitanuova.com/inferno/man/2/sys-file2chan.html.
> of course, somebody has to provide the 9p interface, even
> if that's just posting a fd to /srv.
>
> if you wanted to do something like file2chan in plan 9 and c, you're
> going to have to marshal your data.  this means that chanconnect
> as specified is impossible.  (acme avoids this by using text only.
> the kernel devices keep this under control by using a defined
> byte order and very few binary interfaces.)  i don't know how you would
> solve the naming problems e.g. acme would have using dial-string
> addressing  (i assume that's what you ment; host-port addressing is
> ip specific.).  what would be the port-numbering huristic for allowing
> multiple acmes on the same cpu server?
>
> after whittling away problem cases, i think one is left with pipes,
> and it seems pretty clear how to connect things so that
> chan <-> pipe <-> chan.  one could generalize to multiple
> machines by using tools like cpu(1).

First of all, thanks for all the responses!

I should've mentioned this won't run on top of plan9 (or
Unix).  What I really want is alt!  I brought up RPC but
really, this is just Limbo's "chan of <type>" idea.  In the
concurrent application where I want to use this, it would
factor out a bunch of stuff and simplify communication.

The chanconnect("<host>:<port>") syntax was to get the idea
across.  A real building block might look something like
this:

	int fd = <get a pipe end to something somehow>
	Chan c = fd2chan(fd, <marshalling functions>);

Ideally I'd generate relevant struct definitions and
marshalling functions from the same spec.

-- bakul