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Net::UDP.3pm

NAME

Net::UDP - UDP sockets interface module

SYNOPSIS

     use Net::Gen;               # optional
     use Net::Inet;              # optional
     use Net::UDP;
 
 

DESCRIPTION

The "Net::UDP" module provides services for UDP communications over sockets. It is layered atop the "Net::Inet" and "Net::Gen" modules, which are part of the same distribution.

Public Methods

The following methods are provided by the "Net::UDP" module itself, rather than just being inherited from "Net::Inet" or "Net::Gen".

new

Usage:

     $obj = new Net::UDP;
     $obj = new Net::UDP $desthost, $destservice;
     $obj = new Net::UDP \%parameters;
     $obj = new Net::UDP $desthost, $destservice, \%parameters;
     $obj = 'Net::UDP'->new();
     $obj = 'Net::UDP'->new($desthost);
     $obj = 'Net::UDP'->new($desthost, $destservice);
     $obj = 'Net::UDP'->new(\%parameters);
     $obj = 'Net::UDP'->new($desthost, $destservice, \%parameters);
 
 

Returns a newly-initialised object of the given class. If called for a derived class, no validation of the supplied parameters will be performed. (This is so that the derived class can add the parameter validation it needs to the object before allowing the validation.) Otherwise, it will cause the parameters to be validated by calling its "init" method, which "Net::UDP" inherits from "Net::Inet". In particular, this means that if both a host and a service are given, that an object will only be returned if a connect() call was successful.

The examples above show the indirect object syntax which many prefer, as well as the guaranteed-to-be-safe static method call. There are occasional problems with the indirect object syntax, which tend to be rather obscure when encountered. See http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/1998-01/msg01674.html for details.

PRINT

Usage:

     $ok = $obj->PRINT(@args);
     $ok = print $tied_fh @args;
 
 

This method, intended to be used with tied filehandles, behaves like one of two inherited methods from the "Net::Gen" class, depending on the setting of the object parameter "unbuffered_output". If that parameter is false (the default), then the normal print() builtin is used. If the "unbuffered_output" parameter is true, then each print() operation will actually result in a call to the "send" method, requiring that the object be connected or that its message is in response to its last normal recv() (with a "flags" parameter of 0). The value of the $\ variable is ignored in that case, but the $, variable is still used if the @args array has multiple elements.

READLINE

Usage:

     $line_or_datagram = $obj->READLINE;
     $line_or_datagram = <TIED_FH>;
     $line_or_datagram = readline(TIED_FH);
     @lines_or_datagrams = $obj->READLINE;
     @lines_or_datagrams = <TIED_FH>;
     @lines_or_datagrams = readline(TIED_FH);
 
 

This method, intended to be used with tied filehandles, behaves like one of two inherited methods from the "Net::Gen" class, depending on the setting of the object parameter "unbuffered_input". If that parameter is false (the default), then this method does line-buffering of its input as defined by the current setting of the $/ variable. If the <unbuffered_input> parameter is true, then the input records will be exact recv() datagrams, disregarding the setting of the $/ variable. Note that invoking the "READLINE" method in list context is likely to hang, since UDP sockets typically don't return EOF.

Protected Methods

none.

Known Socket Options

There are no object parameters registered by the "Net::UDP" module itself.

Known Object Parameters

The following object parameters are registered by the "Net::UDP" module (as distinct from being inherited from "Net::Gen" or "Net::Inet"):

unbuffered_input

If true, the "READLINE" operation on tied filehandles will return each recv() buffer as though it were a single separate line, independently of the setting of the $/ variable. The default is false, which causes the "READLINE" interface to return lines split at boundaries as appropriate for $/. (The "READLINE" method for tied filehandles is the "<FH>" operation.) Note that calling the "READLINE" method in list context is likely to hang for UDP sockets.

unbuffered_output

If true, the "PRINT" operation on tied filehandles will result in calls to the send() builtin rather than the print() builtin, as described in ``PRINT'' above. The default is false, which causes the "PRINT" method to use the print() builtin.

unbuffered_IO

This object parameter's value is unreliable on "getparam" or "getparams" method calls. It is provided as a handy way to set both the "unbuffered_output" and "unbuffered_input" object parameters to the same value at the same time during "new" calls.

TIESCALAR support

Tieing of scalars to a UDP handle is supported by inheritance from the "TIESCALAR" method of "Net::Gen". That method only succeeds if a call to a "new" method results in an object for which the "isconnected" method returns true, which is why it is mentioned in regard to this module.

Example:

     tie $x,'Net::UDP',0,'daytime' or die "tie to Net::UDP: $!";
     $x = "\n"; $x = "\n";
     print $y if defined($y = $x);
     untie $x;
 
 

This is an expensive re-implementation of "date" on many machines.

Each assignment to the tied scalar is really a call to the "put" method (via the "STORE" method), and each read from the tied scalar is really a call to the "READLINE" method (via the "FETCH" method).

TIEHANDLE support

As inherited from "Net::Inet" and "Net::Gen", with the addition of unbuffered I/O options for the "READLINE" and "PRINT" methods.

Example:

     tie *FH,'Net::UDP',{unbuffered_IO => 1, thisport => $n, thishost => 0}
         or die;
     while (<FH>) {
         last if is_shutdown_msg($_);
         print FH response($_);
     }
     untie *FH;
 
 

This shows how to make a UDP-based filehandle return (and send) datagrams even when used in the usual perlish paradigm. For some applications, this can be helpful to avoid cluttering the message processing code with the details of handling datagrams. In particular, this example relies on the underlying support for replying to the last address in a recvfrom() for datagram sockets, thus hiding the details of tracking and using that information.

Exports

none

THREADING STATUS

This module has been tested with threaded perls, and should be as thread-safe as perl itself. (As of 5.005_03 and 5.005_57, that's not all that safe just yet.) It also works with interpreter-based threads ('ithreads') in more recent perl releases.

SEE ALSO

Net::Inet(3), Net::Gen(3)

AUTHOR

Spider Boardman <spidb@cpan.org>