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1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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6<meta name="description" content="LuaSocket: SMTP support">
7<meta name="keywords" content="Lua, LuaSocket, SMTP, E-Mail, MIME, Multipart,
8Library, Support">
9<title>LuaSocket: SMTP support</title>
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37
38<!-- smtp +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
39
40<h2 id=smtp>SMTP</h2>
41
42<p> The <tt>smtp</tt> namespace provides functionality to send e-mail
43messages. The high-level API consists of two functions: one to
44define an e-mail message, and another to actually send the message.
45Although almost all users will find that these functions provide more than
46enough functionality, the underlying implementation allows for even more
47control (if you bother to read the code).
48</p>
49
50<p>The implementation conforms to the Simple Mail Transfer Protocol,
51<a href="http://www.ietf.org/rfc/rfc2821.txt">RFC 2821</a>.
52Another RFC of interest is <a
53href="http://www.ietf.org/rfc/rfc2822.txt">RFC 2822</a>,
54which governs the Internet Message Format.
55Multipart messages (those that contain attachments) are part
56of the MIME standard, but described mainly
57in <a href="http://www.ietf.org/rfc/rfc2046.txt">RFC 2046</a>
58
59<p> In the description below, good understanding of <a
60href="http://lua-users.org/wiki/FiltersSourcesAndSinks"> LTN012, Filters
61sources and sinks</a> and the <a href=mime.html>MIME</a> module is
62assumed. In fact, the SMTP module was the main reason for their
63creation. </p>
64
65<p>
66To obtain the <tt>smtp</tt> namespace, run:
67</p>
68
69<pre class=example>
70-- loads the SMTP module and everything it requires
71local smtp = require("socket.smtp")
72</pre>
73
74<p>
75MIME headers are represented as a Lua table in the form:
76</p>
77
78<blockquote>
79<table summary="MIME headers in Lua table">
80<tr><td><tt>
81headers = {<br>
82&nbsp;&nbsp;field-1-name = <i>field-1-value</i>,<br>
83&nbsp;&nbsp;field-2-name = <i>field-2-value</i>,<br>
84&nbsp;&nbsp;field-3-name = <i>field-3-value</i>,<br>
85&nbsp;&nbsp;...<br>
86&nbsp;&nbsp;field-n-name = <i>field-n-value</i><br>
87}
88</tt></td></tr>
89</table>
90</blockquote>
91
92<p>
93Field names are case insensitive (as specified by the standard) and all
94functions work with lowercase field names (but see
95<a href=socket.html#headers.canonic><tt>socket.headers.canonic</tt></a>).
96Field values are left unmodified.
97</p>
98
99<p class=note>
100Note: MIME headers are independent of order. Therefore, there is no problem
101in representing them in a Lua table.
102</p>
103
104<p>
105The following constants can be set to control the default behavior of
106the SMTP module:
107</p>
108
109<ul>
110<li> <tt>DOMAIN</tt>: domain used to greet the server;
111<li> <tt>PORT</tt>: default port used for the connection;
112<li> <tt>SERVER</tt>: default server used for the connection;
113<li> <tt>TIMEOUT</tt>: default timeout for all I/O operations;
114<li> <tt>ZONE</tt>: default time zone.
115</ul>
116
117<!-- send +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
118
119<p class=name id=send>
120smtp.<b>send{</b><br>
121&nbsp;&nbsp;from = <i>string</i>,<br>
122&nbsp;&nbsp;rcpt = <i>string</i> or <i>string-table</i>,<br>
123&nbsp;&nbsp;source = <i>LTN12 source</i>,<br>
124&nbsp;&nbsp;[user = <i>string</i>,]<br>
125&nbsp;&nbsp;[password = <i>string</i>,]<br>
126&nbsp;&nbsp;[server = <i>string</i>,]<br>
127&nbsp;&nbsp;[port = <i>number</i>,]<br>
128&nbsp;&nbsp;[domain = <i>string</i>,]<br>
129&nbsp;&nbsp;[step = <i>LTN12 pump step</i>,]<br>
130&nbsp;&nbsp;[create = <i>function</i>]<br>
131<b>}</b>
132</p>
133
134<p class=description>
135Sends a message to a recipient list. Since sending messages is not as
136simple as downloading an URL from a FTP or HTTP server, this function
137doesn't have a simple interface. However, see the
138<a href=#message><tt>message</tt></a> source factory for
139a very powerful way to define the message contents.
140</p>
141
142
143<p class=parameters>
144The sender is given by the e-mail address in the <tt>from</tt> field.
145<tt>Rcpt</tt> is a Lua table with one entry for each recipient e-mail
146address, or a string
147in case there is just one recipient.
148The contents of the message are given by a <em>simple</em>
149<a href="http://lua-users.org/wiki/FiltersSourcesAndSinks">LTN12</a>
150<tt>source</tt>. Several arguments are optional:
151</p>
152<ul>
153<li> <tt>user</tt>, <tt>password</tt>: User and password for
154authentication. The function will attempt LOGIN and PLAIN authentication
155methods if supported by the server (both are unsafe);
156<li> <tt>server</tt>: Server to connect to. Defaults to "localhost";
157<li> <tt>port</tt>: Port to connect to. Defaults to 25;
158<li> <tt>domain</tt>: Domain name used to greet the server; Defaults to the
159local machine host name;
160<li> <tt>step</tt>:
161<a href="http://lua-users.org/wiki/FiltersSourcesAndSinks">LTN12</a>
162pump step function used to pass data from the
163source to the server. Defaults to the LTN12 <tt>pump.step</tt> function;
164<li><tt>create</tt>: An optional function to be used instead of
165<a href=tcp.html#socket.tcp><tt>socket.tcp</tt></a> when the communications socket is created.
166</ul>
167
168<p class=return>
169If successful, the function returns 1. Otherwise, the function returns
170<b><tt>nil</tt></b> followed by an error message.
171</p>
172
173<p class=note>
174Note: SMTP servers can be very picky with the format of e-mail
175addresses. To be safe, use only addresses of the form
176"<tt>&lt;fulano@example.com&gt;</tt>" in the <tt>from</tt> and
177<tt>rcpt</tt> arguments to the <tt>send</tt> function. In headers, e-mail
178addresses can take whatever form you like. </p>
179
180<p class=note>
181Big note: There is a good deal of misconception with the use of the
182destination address field headers, i.e., the '<tt>To</tt>', '<tt>Cc</tt>',
183and, more importantly, the '<tt>Bcc</tt>' headers. Do <em>not</em> add a
184'<tt>Bcc</tt>' header to your messages because it will probably do the
185exact opposite of what you expect.
186</p>
187
188<p class=note>
189Only recipients specified in the <tt>rcpt</tt> list will receive a copy of the
190message. Each recipient of an SMTP mail message receives a copy of the
191message body along with the headers, and nothing more. The headers
192<em>are</em> part of the message and should be produced by the
193<a href="http://lua-users.org/wiki/FiltersSourcesAndSinks">LTN12</a>
194<tt>source</tt> function. The <tt>rcpt</tt> list is <em>not</em>
195part of the message and will not be sent to anyone.
196</p>
197
198<p class=note>
199<a href="http://www.ietf.org/rfc/rfc2822.txt">RFC 2822</a>
200has two <em>important and short</em> sections, "3.6.3. Destination address
201fields" and "5. Security considerations", explaining the proper
202use of these headers. Here is a summary of what it says:
203</p>
204
205<ul>
206<li> <tt>To</tt>: contains the address(es) of the primary recipient(s)
207of the message;
208<li> <tt>Cc</tt>: (where the "Cc" means "Carbon Copy" in the sense of
209making a copy on a typewriter using carbon paper) contains the
210addresses of others who are to receive the message, though the
211content of the message may not be directed at them;
212<li> <tt>Bcc</tt>: (where the "Bcc" means "Blind Carbon
213Copy") contains addresses of recipients of the message whose addresses are not to be revealed to other recipients of the message.
214</ul>
215
216<p class=note>
217The LuaSocket <tt>send</tt> function does not care or interpret the
218headers you send, but it gives you full control over what is sent and
219to whom it is sent:
220</p>
221<ul>
222<li> If someone is to receive the message, the e-mail address <em>has</em>
223to be in the recipient list. This is the only parameter that controls who
224gets a copy of the message;
225<li> If there are multiple recipients, none of them will automatically
226know that someone else got that message. That is, the default behavior is
227similar to the <tt>Bcc</tt> field of popular e-mail clients;
228<li> It is up to you to add the <tt>To</tt> header with the list of primary
229recipients so that other recipients can see it;
230<li> It is also up to you to add the <tt>Cc</tt> header with the
231list of additional recipients so that everyone else sees it;
232<li> Adding a header <tt>Bcc</tt> is nonsense, unless it is
233empty. Otherwise, everyone receiving the message will see it and that is
234exactly what you <em>don't</em> want to happen!
235</ul>
236
237<p class=note>
238I hope this clarifies the issue. Otherwise, please refer to
239<a href="http://www.ietf.org/rfc/rfc2821.txt">RFC 2821</a>
240and
241<a href="http://www.ietf.org/rfc/rfc2822.txt">RFC 2822</a>.
242</p>
243
244<pre class=example>
245-- load the smtp support
246local smtp = require("socket.smtp")
247
248-- Connects to server "localhost" and sends a message to users
249-- "fulano@example.com", "beltrano@example.com",
250-- and "sicrano@example.com".
251-- Note that "fulano" is the primary recipient, "beltrano" receives a
252-- carbon copy and neither of them knows that "sicrano" received a blind
253-- carbon copy of the message.
254from = "&lt;luasocket@example.com&gt;"
255
256rcpt = {
257 "&lt;fulano@example.com&gt;",
258 "&lt;beltrano@example.com&gt;",
259 "&lt;sicrano@example.com&gt;"
260}
261
262mesgt = {
263 headers = {
264 to = "Fulano da Silva &lt;fulano@example.com&gt;",
265 cc = '"Beltrano F. Nunes" &lt;beltrano@example.com&gt;',
266 subject = "My first message"
267 },
268 body = "I hope this works. If it does, I can send you another 1000 copies."
269}
270
271r, e = smtp.send{
272 from = from,
273 rcpt = rcpt,
274 source = smtp.message(mesgt)
275}
276</pre>
277
278<!-- message ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
279
280<p class=name id=message>
281smtp.<b>message(</b>mesgt<b>)</b>
282</p>
283
284<p class=description>
285Returns a <em>simple</em>
286<a href="http://lua-users.org/wiki/FiltersSourcesAndSinks">LTN12</a> source that sends an SMTP message body, possibly multipart (arbitrarily deep).
287</p>
288
289<p class=parameters>
290The only parameter of the function is a table describing the message.
291<tt>Mesgt</tt> has the following form (notice the recursive structure):
292</p>
293
294<blockquote>
295<table summary="Mesgt table structure">
296<tr><td><tt>
297mesgt = {<br>
298&nbsp;&nbsp;headers = <i>header-table</i>,<br>
299&nbsp;&nbsp;body = <i>LTN12 source</i> or <i>string</i> or
300<i>multipart-mesgt</i><br>
301}<br>
302&nbsp;<br>
303multipart-mesgt = {<br>
304&nbsp;&nbsp;[preamble = <i>string</i>,]<br>
305&nbsp;&nbsp;[1] = <i>mesgt</i>,<br>
306&nbsp;&nbsp;[2] = <i>mesgt</i>,<br>
307&nbsp;&nbsp;...<br>
308&nbsp;&nbsp;[<i>n</i>] = <i>mesgt</i>,<br>
309&nbsp;&nbsp;[epilogue = <i>string</i>,]<br>
310}<br>
311</tt></td></tr>
312</table>
313</blockquote>
314
315<p class=parameters>
316For a simple message, all that is needed is a set of <tt>headers</tt>
317and the <tt>body</tt>. The message <tt>body</tt> can be given as a string
318or as a <em>simple</em>
319<a href="http://lua-users.org/wiki/FiltersSourcesAndSinks">LTN12</a>
320source. For multipart messages, the body is a table that
321recursively defines each part as an independent message, plus an optional
322<tt>preamble</tt> and <tt>epilogue</tt>.
323</p>
324
325<p class=return>
326The function returns a <em>simple</em>
327<a href="http://lua-users.org/wiki/FiltersSourcesAndSinks">LTN12</a>
328source that produces the
329message contents as defined by <tt>mesgt</tt>, chunk by chunk.
330Hopefully, the following
331example will make things clear. When in doubt, refer to the appropriate RFC
332as listed in the introduction. </p>
333
334<pre class=example>
335-- load the smtp support and its friends
336local smtp = require("socket.smtp")
337local mime = require("mime")
338local ltn12 = require("ltn12")
339
340-- creates a source to send a message with two parts. The first part is
341-- plain text, the second part is a PNG image, encoded as base64.
342source = smtp.message{
343 headers = {
344 -- Remember that headers are *ignored* by smtp.send.
345 from = "Sicrano de Oliveira &lt;sicrano@example.com&gt;",
346 to = "Fulano da Silva &lt;fulano@example.com&gt;",
347 subject = "Here is a message with attachments"
348 },
349 body = {
350 preamble = "If your client doesn't understand attachments, \r\n" ..
351 "it will still display the preamble and the epilogue.\r\n" ..
352 "Preamble will probably appear even in a MIME enabled client.",
353 -- first part: no headers means plain text, us-ascii.
354 -- The mime.eol low-level filter normalizes end-of-line markers.
355 [1] = {
356 body = mime.eol(0, [[
357 Lines in a message body should always end with CRLF.
358 The smtp module will *NOT* perform translation. However, the
359 send function *DOES* perform SMTP stuffing, whereas the message
360 function does *NOT*.
361 ]])
362 },
363 -- second part: headers describe content to be a png image,
364 -- sent under the base64 transfer content encoding.
365 -- notice that nothing happens until the message is actually sent.
366 -- small chunks are loaded into memory right before transmission and
367 -- translation happens on the fly.
368 [2] = {
369 headers = {
370 ["content-type"] = 'image/png; name="image.png"',
371 ["content-disposition"] = 'attachment; filename="image.png"',
372 ["content-description"] = 'a beautiful image',
373 ["content-transfer-encoding"] = "BASE64"
374 },
375 body = ltn12.source.chain(
376 ltn12.source.file(io.open("image.png", "rb")),
377 ltn12.filter.chain(
378 mime.encode("base64"),
379 mime.wrap()
380 )
381 )
382 },
383 epilogue = "This might also show up, but after the attachments"
384 }
385}
386
387-- finally send it
388r, e = smtp.send{
389 from = "&lt;sicrano@example.com&gt;",
390 rcpt = "&lt;fulano@example.com&gt;",
391 source = source,
392}
393</pre>
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406</p>
407<p>
408<small>
409Last modified by Diego Nehab on <br>
410Thu Apr 20 00:25:51 EDT 2006
411</small>
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