NAME

       RPC::pClient - Perl extension for writing pRPC clients

SYNOPSIS

         use RPC::pClient;

         $sock = IO::Socket::INET->new('PeerAddr' => 'joes.host.de',
                                       'PeerPort' => 2570,
                                       'Proto' => 'tcp');

         $connection = new RPC::pClient('sock' => $sock,
                                        'application' => 'My App',
                                        'version' => '1.0',
                                        'user' => 'joe',
                                        'password' => 'hello!');

DESCRIPTION

       pRPC (Perl RPC) is a package that simplifies the writing of Perl based client/server
       applications. RPC::pServer is the package used on the server side, and you guess what
       RPC::pClient is for. See RPC::pClient(3) for this part.

       pRPC works by defining a set of of functions that may be executed by the client. For
       example, the server might offer a function "multiply" to the client. Now a function call

           @result = $con->Call('multiply', $a, $b);

       on the client will be mapped to a corresponding call

           multiply($con, $data, $a, $b);

       on the server. (See the funcTable description below for $data.) The function calls result
       will be returned to the client and stored in the array @result. Simple, eh? :-)

   Client methods
       new The client constructor. Returns a client object or an error string, thus you typically
           use it like this:

               $client = RPC::pClient->new ( ... );
               if (!ref($client)) {
                   print STDERR "Error while creating client object: $client\n";
               } else {
                   # Do real stuff
                   ...
               }

       Call
           calls a function on the server; the arguments are a function name, followed by
           function arguments. It returns the function results, if successfull. After executing
           Call() you should always check the error attribute: An empty string indicates success.
           Thus the equivalent to

               $c = Add($a, $b)
               # Use $c
               ...

           is

               $c = $client->Call("Add", $a, $b);
               if ($client->error) {
                   # Do something in case of error
                   ...
               } else {
                   # Use $c
                   ...
               }

       CallInt
           Similar to and internally used by Call. Receives the same arguments, but the result is
           prepended by a status value: If this status value is TRUE, then all went fine and the
           following result array is valid. Otherwise an error occurred and the error message
           follows immediately after the status code. Example:

               my($status, @result) = $client->CallInt("Add", $a, $b);
               if (!$status) {
                   #  Do something in case of error
                   my $errmsg = shift @result  ||  "Unknown error";
                   ...
               } else {
                   ...
               }

       Encrypt
           This method can be used to get or set the cipher attribute, thus the encryption mode.
           If the method is passed an argument, the argument will be used as the new encryption
           mode. ('undef' for no encryption.)  In either case the current encryption mode will be
           returned. Example:

               # Get the current encryption mode
               $mode = $server->Encrypt();

               # Currently disable encryption
               $server->Encrypt(undef);

               # Switch back to the old mode
               $server->Encrypt($mode);

   Client attributes
       Client attributes will typically be supplied with the "new" constructor.

       sock
           An object of type IO::Socket, which should be connected to the server.

       cipher
           This attribute can be used to add encryption quite easily. pRPC is not bound to a
           certain encryption method, but to a block encryption API. The attribute is an object
           supporting the methods blocksize, encrypt and decrypt. For example, the modules
           Crypt::DES and Crypt::IDEA support such an interface.

           Note that you can set or remove encryption on the fly (putting "undef" as attribute
           value will stop encryption), but you have to be sure, that both sides change the
           encryption mode.

           Do not modify this attribute directly, use the encrypt method instead! However, it is
           legal to pass the attribute to the constructor.

           Example:

               use Crypt::DES;
               $crypt = DES->new(pack("H*", "0123456789abcdef"));
               $client->Encrypt($crypt);

               # or, to stop encryption
               $client->Encrypt(undef);

       application
       version
       user
       password
           it is part of the pRPC authorization process, that the client must obeye a login
           procedure where he will pass an application name, a protocol version and optionally a
           user name and password.  You do not care for that (except passing the right values, of
           course :-), this is done within the client constructor.

       io  this attribute is the Storable object created for communication with the server. You
           may use this, for example, when you want to change the encryption mode with
           Storable::Encrypt(). See Storable(3).

EXAMPLE

           #!/usr/local/bin/perl -T
           use 5.0004;               # Yes, this really *is* required.
           use strict;               # Always a good choice.

           use IO::Socket();
           use RPC::pClient;

           # Constants
           my $MY_APPLICATION = "Test Application";
           my $MY_VERSION = 1.0;
           my $MY_USER = "foo";
           my $MY_PASSWORD = "bar";

           # Connect to the server
           my $sock = IO::Socket::INET->new('PeerAddr' => 'joes.host.de',
                                            'PeerPort' => 5000,
                                            'Proto' => 'tcp');
           if (!defined($sock)) {
               die "Cannot connect: $!\n";
           }

           # Login procedure
           my $client = RPC::pClient->new('sock' => $sock,
                                          'application' => $MY_APPLICATION,
                                          'version' => $MY_VERSION,
                                          'user' => $MY_USER,
                                          'password' => $MY_PASSWORD);
           if (!ref($client)) {
               die "Cannot create client: $client\n";
           }

           # Call multiply function
           my $a = $client->Call("multiply", 3, 4);
           if ($client->error) {
               die "An error occurred while multiplying: $a\n";
           }

AUTHOR

       Jochen Wiedmann, wiedmann@neckar-alb.de

SEE ALSO

       pRPC::Server(3), Storable(3), Sys::Syslog(3)

       For an example application, see DBD::pNET(3).