1Net::libnetFAQ(3pm)    Perl Programmers Reference Guide    Net::libnetFAQ(3pm)
2
3
4

NAME

6       libnetFAQ - libnet Frequently Asked Questions
7

DESCRIPTION

9   Where to get this document
10       This document is distributed with the libnet distribution, and is also
11       available on the libnet web page at
12
13           http://search.cpan.org/~gbarr/libnet/
14
15   How to contribute to this document
16       You may mail corrections, additions, and suggestions to me
17       gbarr@pobox.com.
18
20       Copyright (c) 1997-1998 Graham Barr. All rights reserved.  This
21       document is free; you can redistribute it and/or modify it under the
22       terms of the Artistic License.
23
24   Disclaimer
25       This information is offered in good faith and in the hope that it may
26       be of use, but is not guaranteed to be correct, up to date, or suitable
27       for any particular purpose whatsoever.  The authors accept no liability
28       in respect of this information or its use.
29

Obtaining and installing libnet

31   What is libnet ?
32       libnet is a collection of perl5 modules which all related to network
33       programming. The majority of the modules available provided the client
34       side of popular server-client protocols that are used in the internet
35       community.
36
37   Which version of perl do I need ?
38       libnet has been know to work with versions of perl from 5.002 onwards.
39       However if your release of perl is prior to perl5.004 then you will
40       need to obtain and install the IO distribution from CPAN. If you have
41       perl5.004 or later then you will have the IO modules in your
42       installation already, but CPAN may contain updates.
43
44   What other modules do I need ?
45       The only modules you will need installed are the modules from the IO
46       distribution. If you have perl5.004 or later you will already have
47       these modules.
48
49   What machines support libnet ?
50       libnet itself is an entirely perl-code distribution so it should work
51       on any machine that perl runs on. However IO may not work with some
52       machines and earlier releases of perl. But this should not be the case
53       with perl version 5.004 or later.
54
55   Where can I get the latest libnet release
56       The latest libnet release is always on CPAN, you will find it in
57
58        http://www.cpan.org/modules/by-module/Net/
59
60       The latest release and information is also available on the libnet web
61       page at
62
63        http://search.cpan.org/~gbarr/libnet/
64

Using Net::FTP

66   How do I download files from an FTP server ?
67       An example taken from an article posted to comp.lang.perl.misc
68
69           #!/your/path/to/perl
70
71           # a module making life easier
72
73           use Net::FTP;
74
75           # for debugging: $ftp = Net::FTP->new('site','Debug',10);
76           # open a connection and log in!
77
78           $ftp = Net::FTP->new('target_site.somewhere.xxx');
79           $ftp->login('username','password');
80
81           # set transfer mode to binary
82
83           $ftp->binary();
84
85           # change the directory on the ftp site
86
87           $ftp->cwd('/some/path/to/somewhere/');
88
89           foreach $name ('file1', 'file2', 'file3') {
90
91           # get's arguments are in the following order:
92           # ftp server's filename
93           # filename to save the transfer to on the local machine
94           # can be simply used as get($name) if you want the same name
95
96             $ftp->get($name,$name);
97           }
98
99           # ftp done!
100
101           $ftp->quit;
102
103   How do I transfer files in binary mode ?
104       To transfer files without <LF><CR> translation Net::FTP provides the
105       "binary" method
106
107           $ftp->binary;
108
109   How can I get the size of a file on a remote FTP server ?
110   How can I get the modification time of a file on a remote FTP server ?
111   How can I change the permissions of a file on a remote server ?
112       The FTP protocol does not have a command for changing the permissions
113       of a file on the remote server. But some ftp servers may allow a chmod
114       command to be issued via a SITE command, eg
115
116           $ftp->quot('site chmod 0777',$filename);
117
118       But this is not guaranteed to work.
119
120   Can I do a reget operation like the ftp command ?
121   How do I get a directory listing from an FTP server ?
122   Changing directory to "" does not fail ?
123       Passing an argument of "" to ->cwd() has the same affect of calling
124       ->cwd() without any arguments. Turn on Debug (See below) and you will
125       see what is happening
126
127           $ftp = Net::FTP->new($host, Debug => 1);
128           $ftp->login;
129           $ftp->cwd("");
130
131       gives
132
133           Net::FTP=GLOB(0x82196d8)>>> CWD /
134           Net::FTP=GLOB(0x82196d8)<<< 250 CWD command successful.
135
136   I am behind a SOCKS firewall, but the Firewall option does not work ?
137       The Firewall option is only for support of one type of firewall. The
138       type supported is an ftp proxy.
139
140       To use Net::FTP, or any other module in the libnet distribution,
141       through a SOCKS firewall you must create a socks-ified perl executable
142       by compiling perl with the socks library.
143
144   I am behind an FTP proxy firewall, but cannot access machines outside ?
145       Net::FTP implements the most popular ftp proxy firewall approach. The
146       scheme implemented is that where you log in to the firewall with
147       "user@hostname"
148
149       I have heard of one other type of firewall which requires a login to
150       the firewall with an account, then a second login with "user@hostname".
151       You can still use Net::FTP to traverse these firewalls, but a more
152       manual approach must be taken, eg
153
154           $ftp = Net::FTP->new($firewall) or die $@;
155           $ftp->login($firewall_user, $firewall_passwd) or die $ftp->message;
156           $ftp->login($ext_user . '@' . $ext_host, $ext_passwd) or die $ftp->message.
157
158   My ftp proxy firewall does not listen on port 21
159       FTP servers usually listen on the same port number, port 21, as any
160       other FTP server. But there is no reason why this has to be the case.
161
162       If you pass a port number to Net::FTP then it assumes this is the port
163       number of the final destination. By default Net::FTP will always try to
164       connect to the firewall on port 21.
165
166       Net::FTP uses IO::Socket to open the connection and IO::Socket allows
167       the port number to be specified as part of the hostname. So this
168       problem can be resolved by either passing a Firewall option like
169       "hostname:1234" or by setting the "ftp_firewall" option in Net::Config
170       to be a string in in the same form.
171
172   Is it possible to change the file permissions of a file on an FTP server ?
173       The answer to this is "maybe". The FTP protocol does not specify a
174       command to change file permissions on a remote host. However many
175       servers do allow you to run the chmod command via the "SITE" command.
176       This can be done with
177
178         $ftp->site('chmod','0775',$file);
179
180   I have seen scripts call a method message, but cannot find it documented ?
181       Net::FTP, like several other packages in libnet, inherits from
182       Net::Cmd, so all the methods described in Net::Cmd are also available
183       on Net::FTP objects.
184
185   Why does Net::FTP not implement mput and mget methods
186       The quick answer is because they are easy to implement yourself. The
187       long answer is that to write these in such a way that multiple
188       platforms are supported correctly would just require too much code.
189       Below are some examples how you can implement these yourself.
190
191       sub mput {
192         my($ftp,$pattern) = @_;
193         foreach my $file (glob($pattern)) {
194           $ftp->put($file) or warn $ftp->message;
195         } }
196
197       sub mget {
198         my($ftp,$pattern) = @_;
199         foreach my $file ($ftp->ls($pattern)) {
200           $ftp->get($file) or warn $ftp->message;
201         } }
202

Using Net::SMTP

204   Why can't the part of an Email address after the @ be used as the hostname
205       ?
206       The part of an Email address which follows the @ is not necessarily a
207       hostname, it is a mail domain. To find the name of a host to connect
208       for a mail domain you need to do a DNS MX lookup
209
210   Why does Net::SMTP not do DNS MX lookups ?
211       Net::SMTP implements the SMTP protocol. The DNS MX lookup is not part
212       of this protocol.
213
214   The verify method always returns true ?
215       Well it may seem that way, but it does not. The verify method returns
216       true if the command succeeded. If you pass verify an address which the
217       server would normally have to forward to another machine, the command
218       will succeed with something like
219
220           252 Couldn't verify <someone@there> but will attempt delivery anyway
221
222       This command will fail only if you pass it an address in a domain the
223       server directly delivers for, and that address does not exist.
224

Debugging scripts

226   How can I debug my scripts that use Net::* modules ?
227       Most of the libnet client classes allow options to be passed to the
228       constructor, in most cases one option is called "Debug". Passing this
229       option with a non-zero value will turn on a protocol trace, which will
230       be sent to STDERR. This trace can be useful to see what commands are
231       being sent to the remote server and what responses are being received
232       back.
233
234           #!/your/path/to/perl
235
236           use Net::FTP;
237
238           my $ftp = new Net::FTP($host, Debug => 1);
239           $ftp->login('gbarr','password');
240           $ftp->quit;
241
242       this script would output something like
243
244        Net::FTP: Net::FTP(2.22)
245        Net::FTP:   Exporter
246        Net::FTP:   Net::Cmd(2.0801)
247        Net::FTP:   IO::Socket::INET
248        Net::FTP:     IO::Socket(1.1603)
249        Net::FTP:       IO::Handle(1.1504)
250
251        Net::FTP=GLOB(0x8152974)<<< 220 imagine FTP server (Version wu-2.4(5) Tue Jul 29 11:17:18 CDT 1997) ready.
252        Net::FTP=GLOB(0x8152974)>>> user gbarr
253        Net::FTP=GLOB(0x8152974)<<< 331 Password required for gbarr.
254        Net::FTP=GLOB(0x8152974)>>> PASS ....
255        Net::FTP=GLOB(0x8152974)<<< 230 User gbarr logged in.  Access restrictions apply.
256        Net::FTP=GLOB(0x8152974)>>> QUIT
257        Net::FTP=GLOB(0x8152974)<<< 221 Goodbye.
258
259       The first few lines tell you the modules that Net::FTP uses and their
260       versions, this is useful data to me when a user reports a bug. The last
261       seven lines show the communication with the server. Each line has three
262       parts. The first part is the object itself, this is useful for
263       separating the output if you are using multiple objects. The second
264       part is either "<<<<" to show data coming from the server or
265       "&gt&gt&gt&gt" to show data going to the server. The remainder of the
266       line is the command being sent or response being received.
267
269       Copyright (c) 1997 Graham Barr.  All rights reserved.
270
271
272
273perl v5.16.3                      2013-02-26               Net::libnetFAQ(3pm)
Impressum