NAME

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.

What other modules do I need ?

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/');

    foreach $name ('file1', 'file2', 'file3') {

    # get's arguments are in the following order:
    # 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;

this script would output something like

 Net::FTP: Net::FTP(2.22)
 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 <<<< to show data coming from the server or &gt&gt&gt&gt 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.

cpanm mod_perl

perl -MCPAN -e shell
install mod_perl