[ros-users] Generic message transport infrastructure

[Josh Faust]

It doesn't look like any of the problems with the shmem transport have been
fixed (http://code.ros.org/lurker/message/20100510.225110.8f5aa630.en.html),
do you have a plan to do so?

Josh

On Thu, Dec 2, 2010 at 10:05 AM, Cedric Pradalier <
cedric.pradalier at mavt.ethz.ch> wrote:

> After a long time since my first post about a generic message transport
> architecture, we finally released it in the ETHZ-ASL message transport
> stack.
> Details about the ethzasl_message_transport stack can be found at
> http://www.ros.org/wiki/ethzasl_message_transport
>
> In addition to the framework, we also implemented a shared-memory
> transport plugin and a udp multicasting transport plugin, and
> instantiated the transport plugins for images and point-clouds.
>
> The shared memory transport will not offer the same performance as using
> nodelets, but it can be an option when very large object needs to be
> passed around while keeping different processes (there have been several
> discussions on this topic on this list).
>
> The UDP multicasting transport is interesting when small objects needs
> to be passed very quickly to many receivers on several machines (in
> comparison, normal tcp transmission will incur a delay increasing with
> the number of subscribers). Note that the plugin does not manage object
> fragmentation, and does not intend to do it (it would defeat the
> purpose). This means that it will refuse to send object bigger than 8092
> bytes.
>
> Other type-specific transport plugins can quickly be implemented using
> this framework. As examples, I've adapted the theora and compressed
> image transport, and implemented a decimated point cloud transport.
>
> Ideally, the udp multicasting stuff (and shm) should go into the core of
> ROS, but I have not understood enough of the xmlrpc negociation to
> implement it myself.
>
> HTH
>
> --
> Dr. Cedric Pradalier
> http://www.asl.ethz.ch/people/cedricp
>
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>
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