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1 | =head1 NAME |
2 | |
3 | libnetFAQ - libnet Frequently Asked Questions |
4 | |
5 | =head1 DESCRIPTION |
6 | |
7 | =head2 Where to get this document |
8 | |
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9 | This document is distributed with the libnet distribution, and is also |
10 | available on the libnet web page at |
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11 | |
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12 | http://search.cpan.org/~gbarr/libnet/ |
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13 | |
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14 | =head2 How to contribute to this document |
15 | |
16 | You may mail corrections, additions, and suggestions to me |
17 | gbarr@pobox.com. |
18 | |
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19 | =head1 Author and Copyright Information |
20 | |
21 | Copyright (c) 1997-1998 Graham Barr. All rights reserved. |
22 | This document is free; you can redistribute it and/or modify it |
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23 | under the terms of the Artistic License. |
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24 | |
25 | =head2 Disclaimer |
26 | |
27 | This information is offered in good faith and in the hope that it may |
28 | be of use, but is not guaranteed to be correct, up to date, or suitable |
29 | for any particular purpose whatsoever. The authors accept no liability |
30 | in respect of this information or its use. |
31 | |
32 | |
33 | =head1 Obtaining and installing libnet |
34 | |
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35 | =head2 What is libnet ? |
36 | |
37 | libnet is a collection of perl5 modules which all related to network |
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38 | programming. The majority of the modules available provided the |
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39 | client side of popular server-client protocols that are used in |
40 | the internet community. |
41 | |
42 | =head2 Which version of perl do I need ? |
43 | |
44 | libnet has been know to work with versions of perl from 5.002 onwards. However |
45 | if your release of perl is prior to perl5.004 then you will need to |
46 | obtain and install the IO distribution from CPAN. If you have perl5.004 |
47 | or later then you will have the IO modules in your installation already, |
48 | but CPAN may contain updates. |
49 | |
50 | =head2 What other modules do I need ? |
51 | |
52 | The only modules you will need installed are the modules from the IO |
53 | distribution. If you have perl5.004 or later you will already have |
54 | these modules. |
55 | |
56 | =head2 What machines support libnet ? |
57 | |
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58 | libnet itself is an entirely perl-code distribution so it should work |
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59 | on any machine that perl runs on. However IO may not work |
60 | with some machines and earlier releases of perl. But this |
61 | should not be the case with perl version 5.004 or later. |
62 | |
63 | =head2 Where can I get the latest libnet release |
64 | |
65 | The latest libnet release is always on CPAN, you will find it |
66 | in |
67 | |
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68 | http://www.cpan.org/modules/by-module/Net/ |
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69 | |
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70 | The latest release and information is also available on the libnet web page |
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71 | at |
72 | |
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73 | http://search.cpan.org/~gbarr/libnet/ |
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74 | |
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75 | =head1 Using Net::FTP |
76 | |
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77 | =head2 How do I download files from an FTP server ? |
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78 | |
79 | An example taken from an article posted to comp.lang.perl.misc |
80 | |
81 | #!/your/path/to/perl |
82 | |
83 | # a module making life easier |
84 | |
85 | use Net::FTP; |
86 | |
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87 | # for debugging: $ftp = Net::FTP->new('site','Debug',10); |
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88 | # open a connection and log in! |
89 | |
90 | $ftp = Net::FTP->new('target_site.somewhere.xxx'); |
91 | $ftp->login('username','password'); |
92 | |
93 | # set transfer mode to binary |
94 | |
95 | $ftp->binary(); |
96 | |
97 | # change the directory on the ftp site |
98 | |
99 | $ftp->cwd('/some/path/to/somewhere/'); |
100 | |
101 | foreach $name ('file1', 'file2', 'file3') { |
102 | |
103 | # get's arguments are in the following order: |
104 | # ftp server's filename |
105 | # filename to save the transfer to on the local machine |
106 | # can be simply used as get($name) if you want the same name |
107 | |
108 | $ftp->get($name,$name); |
109 | } |
110 | |
111 | # ftp done! |
112 | |
113 | $ftp->quit; |
114 | |
115 | =head2 How do I transfer files in binary mode ? |
116 | |
117 | To transfer files without <LF><CR> translation Net::FTP provides |
118 | the C<binary> method |
119 | |
120 | $ftp->binary; |
121 | |
122 | =head2 How can I get the size of a file on a remote FTP server ? |
123 | |
124 | =head2 How can I get the modification time of a file on a remote FTP server ? |
125 | |
126 | =head2 How can I change the permissions of a file on a remote server ? |
127 | |
128 | The FTP protocol does not have a command for changing the permissions |
129 | of a file on the remote server. But some ftp servers may allow a chmod |
130 | command to be issued via a SITE command, eg |
131 | |
132 | $ftp->quot('site chmod 0777',$filename); |
133 | |
134 | But this is not guaranteed to work. |
135 | |
136 | =head2 Can I do a reget operation like the ftp command ? |
137 | |
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138 | =head2 How do I get a directory listing from an FTP server ? |
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139 | |
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140 | =head2 Changing directory to "" does not fail ? |
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141 | |
142 | Passing an argument of "" to ->cwd() has the same affect of calling ->cwd() |
143 | without any arguments. Turn on Debug (I<See below>) and you will see what is |
144 | happening |
145 | |
146 | $ftp = Net::FTP->new($host, Debug => 1); |
147 | $ftp->login; |
148 | $ftp->cwd(""); |
149 | |
150 | gives |
151 | |
152 | Net::FTP=GLOB(0x82196d8)>>> CWD / |
153 | Net::FTP=GLOB(0x82196d8)<<< 250 CWD command successful. |
154 | |
155 | =head2 I am behind a SOCKS firewall, but the Firewall option does not work ? |
156 | |
157 | The Firewall option is only for support of one type of firewall. The type |
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158 | supported is an ftp proxy. |
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159 | |
160 | To use Net::FTP, or any other module in the libnet distribution, |
161 | through a SOCKS firewall you must create a socks-ified perl executable |
162 | by compiling perl with the socks library. |
163 | |
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164 | =head2 I am behind an FTP proxy firewall, but cannot access machines outside ? |
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165 | |
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166 | Net::FTP implements the most popular ftp proxy firewall approach. The scheme |
167 | implemented is that where you log in to the firewall with C<user@hostname> |
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168 | |
169 | I have heard of one other type of firewall which requires a login to the |
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170 | firewall with an account, then a second login with C<user@hostname>. You can |
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171 | still use Net::FTP to traverse these firewalls, but a more manual approach |
172 | must be taken, eg |
173 | |
174 | $ftp = Net::FTP->new($firewall) or die $@; |
175 | $ftp->login($firewall_user, $firewall_passwd) or die $ftp->message; |
176 | $ftp->login($ext_user . '@' . $ext_host, $ext_passwd) or die $ftp->message. |
177 | |
178 | =head2 My ftp proxy firewall does not listen on port 21 |
179 | |
180 | FTP servers usually listen on the same port number, port 21, as any other |
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181 | FTP server. But there is no reason why this has to be the case. |
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182 | |
183 | If you pass a port number to Net::FTP then it assumes this is the port |
184 | number of the final destination. By default Net::FTP will always try |
185 | to connect to the firewall on port 21. |
186 | |
187 | Net::FTP uses IO::Socket to open the connection and IO::Socket allows |
188 | the port number to be specified as part of the hostname. So this problem |
189 | can be resolved by either passing a Firewall option like C<"hostname:1234"> |
190 | or by setting the C<ftp_firewall> option in Net::Config to be a string |
191 | in in the same form. |
192 | |
193 | =head2 Is it possible to change the file permissions of a file on an FTP server ? |
194 | |
195 | The answer to this is "maybe". The FTP protocol does not specify a command to change |
196 | file permissions on a remote host. However many servers do allow you to run the |
197 | chmod command via the C<SITE> command. This can be done with |
198 | |
199 | $ftp->site('chmod','0775',$file); |
200 | |
201 | =head2 I have seen scripts call a method message, but cannot find it documented ? |
202 | |
203 | Net::FTP, like several other packages in libnet, inherits from Net::Cmd, so |
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204 | all the methods described in Net::Cmd are also available on Net::FTP |
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205 | objects. |
206 | |
207 | =head2 Why does Net::FTP not implement mput and mget methods |
208 | |
209 | The quick answer is because they are easy to implement yourself. The long |
210 | answer is that to write these in such a way that multiple platforms are |
211 | supported correctly would just require too much code. Below are |
212 | some examples how you can implement these yourself. |
213 | |
214 | sub mput { |
215 | my($ftp,$pattern) = @_; |
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216 | foreach my $file (glob($pattern)) { |
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217 | $ftp->put($file) or warn $ftp->message; |
218 | } |
219 | } |
220 | |
221 | sub mget { |
222 | my($ftp,$pattern) = @_; |
223 | foreach my $file ($ftp->ls($pattern)) { |
224 | $ftp->get($file) or warn $ftp->message; |
225 | } |
226 | } |
227 | |
228 | |
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229 | =head1 Using Net::SMTP |
230 | |
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231 | =head2 Why can't the part of an Email address after the @ be used as the hostname ? |
232 | |
233 | The part of an Email address which follows the @ is not necessarily a hostname, |
234 | it is a mail domain. To find the name of a host to connect for a mail domain |
235 | you need to do a DNS MX lookup |
236 | |
237 | =head2 Why does Net::SMTP not do DNS MX lookups ? |
238 | |
239 | Net::SMTP implements the SMTP protocol. The DNS MX lookup is not part |
240 | of this protocol. |
241 | |
242 | =head2 The verify method always returns true ? |
243 | |
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244 | Well it may seem that way, but it does not. The verify method returns true |
245 | if the command succeeded. If you pass verify an address which the |
246 | server would normally have to forward to another machine, the command |
247 | will succeed with something like |
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248 | |
249 | 252 Couldn't verify <someone@there> but will attempt delivery anyway |
250 | |
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251 | This command will fail only if you pass it an address in a domain |
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252 | the server directly delivers for, and that address does not exist. |
253 | |
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254 | =head1 Debugging scripts |
255 | |
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256 | =head2 How can I debug my scripts that use Net::* modules ? |
257 | |
258 | Most of the libnet client classes allow options to be passed to the |
259 | constructor, in most cases one option is called C<Debug>. Passing |
260 | this option with a non-zero value will turn on a protocol trace, which |
261 | will be sent to STDERR. This trace can be useful to see what commands |
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262 | are being sent to the remote server and what responses are being |
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263 | received back. |
264 | |
265 | #!/your/path/to/perl |
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266 | |
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267 | use Net::FTP; |
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268 | |
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269 | my $ftp = new Net::FTP($host, Debug => 1); |
270 | $ftp->login('gbarr','password'); |
271 | $ftp->quit; |
272 | |
273 | this script would output something like |
274 | |
275 | Net::FTP: Net::FTP(2.22) |
276 | Net::FTP: Exporter |
277 | Net::FTP: Net::Cmd(2.0801) |
278 | Net::FTP: IO::Socket::INET |
279 | Net::FTP: IO::Socket(1.1603) |
280 | Net::FTP: IO::Handle(1.1504) |
281 | |
282 | Net::FTP=GLOB(0x8152974)<<< 220 imagine FTP server (Version wu-2.4(5) Tue Jul 29 11:17:18 CDT 1997) ready. |
283 | Net::FTP=GLOB(0x8152974)>>> user gbarr |
284 | Net::FTP=GLOB(0x8152974)<<< 331 Password required for gbarr. |
285 | Net::FTP=GLOB(0x8152974)>>> PASS .... |
286 | Net::FTP=GLOB(0x8152974)<<< 230 User gbarr logged in. Access restrictions apply. |
287 | Net::FTP=GLOB(0x8152974)>>> QUIT |
288 | Net::FTP=GLOB(0x8152974)<<< 221 Goodbye. |
289 | |
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290 | The first few lines tell you the modules that Net::FTP uses and their versions, |
291 | this is useful data to me when a user reports a bug. The last seven lines |
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292 | show the communication with the server. Each line has three parts. The first |
293 | part is the object itself, this is useful for separating the output |
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294 | if you are using multiple objects. The second part is either C<<<<<> to |
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295 | show data coming from the server or C<>>>>> to show data |
296 | going to the server. The remainder of the line is the command |
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297 | being sent or response being received. |
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298 | |
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299 | =head1 AUTHOR AND COPYRIGHT |
300 | |
301 | Copyright (c) 1997 Graham Barr. |
302 | All rights reserved. |
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303 | |
304 | =for html <hr> |
305 | |
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306 | I<$Id: //depot/libnet/Net/libnetFAQ.pod#6 $> |
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307 | |