libnetFAQ - libnet Frequently Asked Questions
Where to get this document
This document is distributed with the libnet disribution,
and is also avaliable on the libnet web page at
http://www.connect.net/gbarr/libnet/
How to contribute to this document
You may mail corrections, additions, and suggestions to me
gbarr@pobox.com.
Author and Copyright Information
Copyright (c) 1997 Graham Barr. All rights reserved.
Non-commercial Reproduction
Permission is granted to distribute this document, in part
or in full, via electronic means or printed copy providing
that (1) that all credits and copyright notices be
retained, (2) that no charges beyond reproduction be
involved, and (3) that a reasonable attempt be made to use
the most current version available.
Disclaimer
This information is offered in good faith and in the hope
that it may be of use, but is not guaranteed to be
correct, up to date, or suitable for any particular
purpose whatsoever. The authors accept no liability in
respect of this information or its use.
Obtaining and installing libnet
What is libnet ?
libnet is a collection of perl5 modules which all related
to network programming. The majority of the modules
avaliable provided the client side of popular server-
client protocols that are used in the internet community.
Which version of perl do I need ?
libnet has been know to work with versions of perl from
5.002 onwards. However if your release of perl is prior to
perl5.004 then you will need to obtain and install the IO
distribution from CPAN. If you have perl5.004 or later
then you will have the IO modules in your installation
already, but CPAN may contain updates.
The only modules you will need installed are the modules
from the IO distribution. If you have perl5.004 or later
you will already have these modules.
What machines support libnet ?
libnet itself is an entirly perl-code distribution so it
should work on any machine that perl runs on. However IO
may not work with some machines and earlier releases of
perl. But this should not be the case with perl version
5.004 or later.
Where can I get the latest libnet release
The latest libnet release is always on CPAN, you will find
it in
http://www.perl.com/CPAN/modules/by-module/Net/
The latest release and information is also avaliable on the libnet web page
at
http://www.connect.net/gbarr/libnet/
Using Net::FTP
How do I download files from a FTP server
An example taken from an articlt posted to
comp.lang.perl.misc
#!/your/path/to/perl
# a module making life easier
use Net::FTP;
# for debuging: $ftp = Net::FTP->new('site','Debug',10);
# open a connection and log in!
$ftp = Net::FTP->new('target_site.somewhere.xxx');
$ftp->login('username','password');
# set transfer mode to binary
$ftp->binary();
# change the directory on the ftp site
$ftp->cwd('/some/path/to/somewhere/');
# ftp server's filename
# filename to save the transfer to on the local machine
# can be simply used as get($name) if you want the same name
$ftp->get($name,$name);
}
# ftp done!
$ftp->quit;
How do I transfer files in binary mode ?
To transfer files without <LF><CR> translation Net::FTP
provides the binary method
$ftp->binary;
How can I can the size of a file on a remote FTP server ?
How can I can the modification time of a file on a remote
FTP server ?
Can I do a reget operation like the ftp command ?
How do I get a directory listing from a FTP server ?
Debugging scripts
How can I debug my scripts that use Net::* modules ?
Most of the libnet client classes allow options to be
passed to the constructor, in most cases one option is
called Debug. Passing this option with a non-zero value
will turn on a protocol trace, which will be sent to
STDERR. This trace can be useful to see what commands are
being sent to the remote server and what responces are
being received back.
#!/your/path/to/perl
use Net::FTP;
my $ftp = new Net::FTP($host, Debug => 1);
$ftp->login('gbarr','password');
$ftp->quit;
Net::FTP: Exporter
Net::FTP: Net::Cmd(2.0801)
Net::FTP: IO::Socket::INET
Net::FTP: IO::Socket(1.1603)
Net::FTP: IO::Handle(1.1504)
Net::FTP=GLOB(0x8152974)<<< 220 imagine FTP server (Version wu-2.4(5) Tue Jul 29 11:17:18 CDT 1997) ready.
Net::FTP=GLOB(0x8152974)>>> user gbarr
Net::FTP=GLOB(0x8152974)<<< 331 Password required for gbarr.
Net::FTP=GLOB(0x8152974)>>> PASS ....
Net::FTP=GLOB(0x8152974)<<< 230 User gbarr logged in. Access restrictions apply.
Net::FTP=GLOB(0x8152974)>>> QUIT
Net::FTP=GLOB(0x8152974)<<< 221 Goodbye.
The first few lines tell you the modules that Net::FTP
uses and thier versions, this is usefule data to me when a
user reports a bug. The last seven lines show the
communication with the server. Each line has three parts.
The first part is the object itself, this is useful for
separating the output if you are using mutiple objects.
The second part is either C<<<<<> to show data coming from
the server or >>>> to show data going to the
server. The remainder of the line is the command being
sent or responce being received.
Copyright (c) 1997 Graham Barr. All rights reserved.