Net::libnetFAQ - phpMan

NAME
    libnetFAQ - libnet Frequently Asked Questions

DESCRIPTION
  Where to get this document
    This document is distributed with the libnet distribution, and is also
    available on the libnet web page at

    <https://metacpan.org/release/libnet>

  How to contribute to this document
    You may report corrections, additions, and suggestions on the CPAN
    Request Tracker at

    <https://rt.cpan.org/Public/Bug/Report.html?Queue=libnet>

Author and Copyright Information
    Copyright (C) 1997-1998 Graham Barr. All rights reserved. This document
    is free; you can redistribute it and/or modify it under the same terms
    as Perl itself, i.e. under the terms of either the GNU General Public
    License or the Artistic License, as specified in the LICENCE file.

    Steve Hay <shay AT cpan.org <mailto:shay AT cpan.org>> is now maintaining
    libnet as of version 1.22_02.

  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 available provided the client
    side of popular server-client protocols that are used in the internet
    community.

  Which version of perl do I need ?
    This version of libnet requires Perl 5.8.1 or higher.

  What other modules do I need ?
    No non-core modules are required for normal use, except on os390, which
    requires Convert::EBCDIC.

    Authen::SASL is required for AUTH support.

    IO::Socket::SSL version 2.007 or higher is required for SSL support.

    IO::Socket::IP version 0.25 or IO::Socket::INET6 version 2.62 is
    required for IPv6 support.

  What machines support libnet ?
    libnet itself is an entirely perl-code distribution so it should work on
    any machine that perl runs on.

  Where can I get the latest libnet release
    The latest libnet release is always on CPAN, you will find it in

    <https://metacpan.org/release/libnet>

Using Net::FTP
  How do I download files from an FTP server ?
    An example taken from an article posted to comp.lang.perl.misc

        #!/your/path/to/perl

        # a module making life easier

        use Net::FTP;

        # for debugging: $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 get the size of a file on a remote FTP server ?
  How can I get the modification time of a file on a remote FTP server ?
  How can I change the permissions of a file on a remote server ?
    The FTP protocol does not have a command for changing the permissions of
    a file on the remote server. But some ftp servers may allow a chmod
    command to be issued via a SITE command, eg

        $ftp->quot('site chmod 0777',$filename);

    But this is not guaranteed to work.

  Can I do a reget operation like the ftp command ?
  How do I get a directory listing from an FTP server ?
  Changing directory to "" does not fail ?
    Passing an argument of "" to ->cwd() has the same affect of calling
    ->cwd() without any arguments. Turn on Debug (*See below*) and you will
    see what is happening

        $ftp = Net::FTP->new($host, Debug => 1);
        $ftp->login;
        $ftp->cwd("");

    gives

        Net::FTP=GLOB(0x82196d8)>>> CWD /
        Net::FTP=GLOB(0x82196d8)<<< 250 CWD command successful.

  I am behind a SOCKS firewall, but the Firewall option does not work ?
    The Firewall option is only for support of one type of firewall. The
    type supported is an ftp proxy.

    To use Net::FTP, or any other module in the libnet distribution, through
    a SOCKS firewall you must create a socks-ified perl executable by
    compiling perl with the socks library.

  I am behind an FTP proxy firewall, but cannot access machines outside ?
    Net::FTP implements the most popular ftp proxy firewall approach. The
    scheme implemented is that where you log in to the firewall with
    "user@hostname"

    I have heard of one other type of firewall which requires a login to the
    firewall with an account, then a second login with "user@hostname". You
    can still use Net::FTP to traverse these firewalls, but a more manual
    approach must be taken, eg

        $ftp = Net::FTP->new($firewall) or die $@;
        $ftp->login($firewall_user, $firewall_passwd) or die $ftp->message;
        $ftp->login($ext_user . '@' . $ext_host, $ext_passwd) or die $ftp->message.

  My ftp proxy firewall does not listen on port 21
    FTP servers usually listen on the same port number, port 21, as any
    other FTP server. But there is no reason why this has to be the case.

    If you pass a port number to Net::FTP then it assumes this is the port
    number of the final destination. By default Net::FTP will always try to
    connect to the firewall on port 21.

    Net::FTP uses IO::Socket to open the connection and IO::Socket allows
    the port number to be specified as part of the hostname. So this problem
    can be resolved by either passing a Firewall option like "hostname:1234"
    or by setting the "ftp_firewall" option in Net::Config to be a string in
    the same form.

  Is it possible to change the file permissions of a file on an FTP server ?
    The answer to this is "maybe". The FTP protocol does not specify a
    command to change file permissions on a remote host. However many
    servers do allow you to run the chmod command via the "SITE" command.
    This can be done with

      $ftp->site('chmod','0775',$file);

  I have seen scripts call a method message, but cannot find it documented ?
    Net::FTP, like several other packages in libnet, inherits from Net::Cmd,
    so all the methods described in Net::Cmd are also available on Net::FTP
    objects.

  Why does Net::FTP not implement mput and mget methods
    The quick answer is because they are easy to implement yourself. The
    long answer is that to write these in such a way that multiple platforms
    are supported correctly would just require too much code. Below are some
    examples how you can implement these yourself.

    sub mput { my($ftp,$pattern) = @_; foreach my $file (glob($pattern)) {
    $ftp->put($file) or warn $ftp->message; } }

    sub mget { my($ftp,$pattern) = @_; foreach my $file ($ftp->ls($pattern))
    { $ftp->get($file) or warn $ftp->message; } }

Using Net::SMTP
  Why can't the part of an Email address after the @ be used as the hostname ?
    The part of an Email address which follows the @ is not necessarily a
    hostname, it is a mail domain. To find the name of a host to connect for
    a mail domain you need to do a DNS MX lookup

  Why does Net::SMTP not do DNS MX lookups ?
    Net::SMTP implements the SMTP protocol. The DNS MX lookup is not part of
    this protocol.

  The verify method always returns true ?
    Well it may seem that way, but it does not. The verify method returns
    true if the command succeeded. If you pass verify an address which the
    server would normally have to forward to another machine, the command
    will succeed with something like

        252 Couldn't verify <someone@there> but will attempt delivery anyway

    This command will fail only if you pass it an address in a domain the
    server directly delivers for, and that address does not exist.

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 responses 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 their
    versions, this is useful 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 multiple 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 response being received.

AUTHOR AND COPYRIGHT
    Copyright (C) 1997-1998 Graham Barr. All rights reserved.