RPC::pClient - Perl extension for writing pRPC clients

  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!');

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 CW$data.) The function calls result will be returned to the client and stored in the array CW@result. Simple, eh? :-)

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 will typically be supplied with the CWnew 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 CWundef 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).

    #!/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";
    }

Jochen Wiedmann, wiedmann@neckar-alb.de

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

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