Install Rasplex. First time

Install Rasplex 0.5.1 on my raspberry pi with manual http://www.rasplex.com/get-started/rasplex-installers.html

When go to getdirectory on menu I see an error:

 

OnJobComplete failed to find a server on http://0.0.0.0:32400/

 

why? It's necessary to install any more software?

I don't know if this is your problem, but from the same website you linked to

http://www.rasplex.com/docs/setup.html

Step 1: Setup Plex

Plex Media Server is required to be installed on your home computer in order to use RasPlex.

Install Rasplex 0.5.1 on my raspberry pi with manual http://www.rasplex.com/get-started/rasplex-installers.html

When go to getdirectory on menu I see an error:

OnJobComplete failed to find a server on http://0.0.0.0:32400/

why? It's necessary to install any more software?

Your description of the problem lacks most of the details we would need to understand it fully, so we have to guess at the rest.

One of those guesses (also shared by OttoKerner in his post) is that you may be new to the entire Plex server-client concept.

Unlike other media player implementations a Plex client is NOT intended for playback of media accessed directly by that client.

Instead it is intended to receive ALL media streams from a server, usually the PMS server of a Plex account owned by the client owner.

(Here PMS == Plex Media Server)

Other use cases also exist, such as receiving media streams from the PMS server of a friend's account, or even from unrelated servers on the Internet through so-called 'Plex Channels', but even for the latter each such channel connection is mediated by a PMS server.
 

In short: Without some Plex server to connect to, somewhere on Internet or on your LAN, any Plex client is pretty much useless.

(Except if you had such a connection previously, and 'synced' parts of its media library to local sync cache, which PHT/RasPlex is not intended for.)

Even for cases where all the media you want to access is to be streamed from a friend's server, you still need a Plex account of your own, which you must specify login data for in your Plex clients (such as RasPlex) since sharing of media through Plex is always done via account identification (though specifying it can be optional for clients on same LAN as the PMS server they use, depending on the server configuration).

If you only wish to play media local to your LAN through normal PC/NAS filesharing, without installing a Plex server, then you should use the standard OpenELEC release or something similar (like XBian, or standard Raspbian+XBMC) instead of RasPlex.

Best regards: dlanor