Section: User Contributed Perl Documentation (3)
Updated: 2006-04-23
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Event::RPC - Event based transparent Client/Server RPC framework  


  #-- Server Code
  use Event::RPC::Server;
  use My::TestModule;
  my $server = Event::RPC::Server->new (
      port    => 5555,
      classes => { "My::TestModule" => { ... } },


  #-- Client Code
  use Event::RPC::Client;
  my $client = Event::RPC::Client->new (
      server   => "localhost",
      port     => 5555,

  #-- Call methods of My::TestModule on the server
  my $obj = My::TestModule->new ( foo => "bar" );
  my $foo = $obj->get_foo;



Event::RPC supports you in developing Event based networking client/server applications with transparent object/method access from the client to the server. Network communication is optionally encrypted using IO::Socket::SSL. Several event loop managers are supported due to an extensible API. Currently Event and Glib are implemented.  


Event::RPC consists of a server and a client library. The server exports a list of classes and methods, which are allowed to be called over the network. More specific it acts as a proxy for objects created on the server side (on demand of the connected clients) which handles client side methods calls with transport of method arguments and return values.

The object proxy handles refcounting and destruction of objects created by clients properly. Objects as method parameters and return values are handled as well (although with some limitations, see below).

For the client the whole thing is totally transparent - once connected to the server it doesn't know whether it calls methods on local or remote objects.

Also the methods on the server newer know whether they are called locally or from a connected client. Your application logic is not affected by Event::RPC at all, at least if it has a rudimentary clean OO design.

For details on implementing servers and clients please refer to the man pages of Event::RPC::Server and Event::RPC::Client.  


Event::RPC needs either one of the following modules on the server (they're not necessary on the client):


They're needed for event handling resp. mainloop implementation. If you like to use SSL encryption you need to install


As well Event::RPC makes heavy use of the


module, which is part of the Perl standard library. It's important that both client and server use exactly the same version of the Storable module! Otherwise Event::RPC client/server communication will fail badly.  


You get the latest installation tarballs and online documentation at this location:


If your system meets the requirements mentioned above, installation is just:

  perl Makefile.PL
  make test
  make install



The tarball includes an examples/ directory which contains two programs:


Just execute them with --help to get the usage. They do some very simple communication but are good to test your setup, in particular in a mixed environment.  


Although the classes and objects on the server are accessed transparently by the client there are some limitations should be aware of. With a clean object oriented design these should be no problem in real applications:  

Direct object data manipulation is forbidden

All objects reside on the server and they keep there! The client just has specially wrapped proxy objects, which trigger the necessary magic to access the object's methods on the server. Complete objects are never transferred from the server to the client, so something like this does not work:

  $object->{data} = "changed data";

(assuming $object is a hash ref on the server).

Only method calls are transferred to the server, so even for ``simple'' data manipulation a method call is necessary:

  $object->set_data ("changed data");

As well for reading an object attribute. Accessing a hash key will fail:

  my $data = $object->{data};

Instead call a method which returns the 'data' member:

  my $data = $object->get_data;


Methods may exchange objects, but not in a too complex structure

Event::RPC handles methods which return objects. The only requirement is that they are declared as a Object returner on the server (refer to Event::RPC::Server for details), but not if the object is hided inside a deep complex data structure.

An array or hash ref of objects is Ok, but not more. This would require to much expensive runtime data inspection.

Object receiving parameters are more restrictive, since even hiding them inside one array or hash ref is not allowed. They must be passed as a direkt argument of the method subroutine.  


  Jörn Reder <joern at zyn dot de>



Copyright (C) 2002-2006 by Joern Reder, All Rights Reserved.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.



Direct object data manipulation is forbidden
Methods may exchange objects, but not in a too complex structure

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