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).