data transfer via bus daemon

[Alexander Larsson]

On Fri, 2007-09-21 at 08:49 +0200, Thiago Macieira wrote:
> Pa1 K wrote:
> >So if two processes are communicating via bus daemon, using TCP sockets,
> >then there will be 2 TCP connections- 1. process A to bus daemon; 2
> > process B to bus daemon. If we need to transfer large amount of data in
> > this setup, is it a ideal solution to use? OR is it possible in Dbus
> > for two applications to transfer data directly between each other,
> > after discovering each other via the bus, and then bypassing the bus.
> > And thus the overhead of two TCP connections is reduced to one TCP
> > connection.
> 
> That is what I recommend: once the two applications discover each other, 
> they should open a faster channel for transferring a large bulk of data. 
> Transferring it over the daemon is very inefficient.

DBus isn't enourmously fast for bulk transfers, even in the peer-to-peer
mode. What I do in gvfs is discover the gvfs daemons via the session
bus, then I create peer-to-peer connections directly to the daemons for
"metadata" operations like readdir and stat, but for bulk file data
transfers (saving or loading a file) we pass a socketpair fd to the
client and use a binary lowlevel protocol.