rsync - Apr 2014 - rsync's usage of ssh

I am trying to understand how rsync uses ssh. From what I understand of
the source, it simply opens a ssh connection and then simply pipes
rsync's data. But somehow my stomach tells me that this is not the whole
story.

For one, that would mean the whole (?) of rsync's protocol is only used
for not-ssh transmission. The biggest question for me right now is,
whether rsync, when transmitting remotely over ssh, is binding sockets
of some kind or if it is completely dependent on ssh for that.

For every bit of enlightenment in this regard I am very grateful!

alex.

On 12.04.2014 20:48, a. wrote:
> I am trying to understand how rsync uses ssh. From what I understand of
> the source, it simply opens a ssh connection and then simply pipes
> rsync's data. But somehow my stomach tells me that this is not the
whole
> story.
> 
> For one, that would mean the whole (?) of rsync's protocol is only used
> for not-ssh transmission. The biggest question for me right now is,
> whether rsync, when transmitting remotely over ssh, is binding sockets
> of some kind or if it is completely dependent on ssh for that.
> 
> For every bit of enlightenment in this regard I am very grateful!
rsync always works with 2 processes connected by a bidirectional 
connection, even when run localy.

Rsync can use any method that provides such a bidirectional connection. 
Using ssh is only the "standard" way to do it.

rsync is either used like this:
Locally: rsync a <-> rsync b
Or like this:
Remote: rsync a <-> connector (e.g. ssh) <-> rsync b

<-> means a bidirectional connection.

Specifically or in effect it means that STDOUT from a is connected to 
STDIN from b and vice versa.




-- 

Matthias