luasocket/doc/smtp.html

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<title>LuaSocket: Network support for the Lua language</title>
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<tr><td align=center valign=top>Network support for the Lua language
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<!-- smtp +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<h2 id=smtp>SMTP</h2>
<p> The <tt>smtp.lua</tt> module provides functionality to send e-mail
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messages. The implementation conforms to the Simple Mail Transfer Protocol,
<a href="http://www.cs.princeton.edu/~diego/rfc/rfc2821.txt">RFC 2821</a>.
Another RFC of interest is <a
href="http://www.cs.princeton.edu/~diego/rfc/rfc2822.txt">RFC 2822</a>,
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which governs the Internet Message Format.
Multipart messages (those that contain attatchments) are part
of the MIME standard, but described mainly
in <a href="http://www.cs.princeton.edu/~diego/rfc/rfc2046.txt">RFC
2046</a>
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<p> In the description below, good understanding of <a
href="http://lua-users.org/wiki/FiltersSourcesAndSinks"> LTN012, Filters
sources and sinks</a> and the <a href=mime.html>MIME</a> module is
assumed. In fact, the SMTP module was the main reason for their
creation. </p>
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<p>
MIME headers are represented as a Lua table in the form:
</p>
<blockquote>
<table summary="MIME headers in Lua table">
<tr><td><tt>
headers = {<br>
&nbsp;&nbsp;field-1-name = <i>field-1-value</i>,<br>
&nbsp;&nbsp;field-2-name = <i>field-2-value</i>,<br>
&nbsp;&nbsp;field-3-name = <i>field-3-value</i>,
</tt></td></tr>
<tr><td align=center><tt>
&nbsp;&nbsp;...
</tt></td></tr>
<tr><td><tt>
&nbsp;&nbsp;field-n-name = <i>field-n-value</i><br>
}
</tt></td></tr>
</table>
</blockquote>
<p>
Field names are case insensitive (as specified by the standard) and all
functions work with lowercase field names.
Field values are left unmodified.
</p>
<p class=note>
Note: MIME headers are independent of order. Therefore, there is no problem
in representing them in a Lua table.
</p>
<p>
The following constants can be set to control the default behaviour of
the SMTP module:
</p>
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<ul>
<li> <tt>DOMAIN</tt>: domain used to greet the server;
<li> <tt>PORT</tt>: default port used for the connection;
<li> <tt>SERVER</tt>: default server used for the connection;
<li> <tt>TIMEOUT</tt>: default timeout for all I/O operations;
<li> <tt>ZONE</tt>: default time zone.
</ul>
<!-- send +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class=name id=send>
smtp.<b>send{</b><br>
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&nbsp;&nbsp;from = <i>string</i>,<br>
&nbsp;&nbsp;rcpt = <i>string</i> or <i>string-table</i>,<br>
&nbsp;&nbsp;source = <i>LTN12 source</i>,<br>
&nbsp;&nbsp;[server = <i>string</i>],<br>
&nbsp;&nbsp;[port = <i>string</i>]<br>
&nbsp;&nbsp;[domain = <i>string</i>],<br>
&nbsp;&nbsp;[step = <i>LTN12 pump step</i>],<br>
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<b>}</b>
</p>
<p class=description>
Sends a message to a recipient list. Since sending messages is not as
simple as downloading an URL from a FTP or HTTP server, this function
doesn't have a simple interface. However, see the
<a href=#message><tt>message</tt></a> source factory for
a very powerful way to define the message contents.
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</p>
<p class=parameters>
The sender is given by the e-mail address in the <tt>from</tt> field.
<tt>Rcpt</tt> is a Lua table with one entry for each recipient e-mail
address, or a string
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in case there is just one recipient.
The contents of the message are given by a LTN12 <tt>source</tt>. Several
arguments are optional:
<ul>
<li> <tt>server</tt>: Server to connect to. Defaults to "localhost";
<li> <tt>port</tt>: Port to connect to. Defaults to 25;
<li> <tt>domain</tt>: Domain name used to greet the server; Defaults to the
local machine host name;
<li> <tt>step</tt>: LTN12 pump step function used to pass data from the
source to the server. Defaults to the LTN12 <tt>pump.step</tt> function.
</ul>
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</p>
<p class=return>
If successful, the function returns 1. Otherwise, the function returns
<b><tt>nil</tt></b> followed by an error message.
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</p>
<p class=note>
Note: SMTP servers are can be very picky with the format of e-mail
addresses. To be safe, use only addresses of the form
"<tt>&lt;fulano@tecgraf.puc-rio.br&gt;</tt>" in the <tt>from</tt> and
<tt>rcpt</tt> arguments to the <tt>send</tt> function. In headers, e-mail
addresses can take whatever form you like. </p>
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<p class=note>
Big note: There is a good deal of misconception with the use of the
destination address field headers, i.e., the '<tt>To</tt>', '<tt>Cc</tt>',
and, more importantly, the '<tt>Bcc</tt>' headers. Do <em>not</em> add a
'<tt>Bcc</tt>' header to your messages because it will probably do the
exact opposite of what you expect.
</p>
<p class=note>
Only recipients specified in the <tt>rcpt</tt> list will receive a copy of the
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message. Each recipient of an SMTP mail message receives a copy of the
message body along with the headers, and nothing more. The headers
<em>are</em> part of the message and should be produced by the LTN12
<tt>source</tt> function. The <tt>rcpt</tt> list is <em>not</em>
part of the message and will not be sent to anyone.
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</p>
<p class=note>
<a href="http://www.cs.princeton.edu/~diego/rfc/rfc2822.txt">RFC 2822</a>
has two <em>important and short</em> sections, "3.6.3. Destination address
fields" and "5. Security considerations", explaining the proper
use of these headers. Here is a summary of what it says:
</p>
<ul>
<li> <tt>To</tt>: contains the address(es) of the primary recipient(s)
of the message;
<li> <tt>Cc</tt>: (where the "Cc" means "Carbon Copy" in the sense of
making a copy on a typewriter using carbon paper) contains the
addresses of others who are to receive the message, though the
content of the message may not be directed at them;
<li> <tt>Bcc</tt>: (where the "Bcc" means "Blind Carbon
Copy") contains addresses of recipients of the message whose addresses are not to be revealed to other recipients of the message.
</ul>
<p class=note>
The LuaSocket <tt>send</tt> function does not care or interpret the
headers you send, but it gives you full control over what is sent and
to whom it is sent:
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</p>
<ul>
<li> If someone is to receive the message, the e-mail address <em>has</em>
to be in the recipient list. This is the only parameter that controls who
gets a copy of the message;
<li> If there are multiple recipients, none of them will automatically
know that someone else got that message. That is, the default behavior is
similar to the <tt>Bcc</tt> field of popular e-mail clients;
<li> It is up to you to add the <tt>To</tt> header with the list of primary
recipients so that other recipients can see it;
<li> It is also up to you to add the <tt>Cc</tt> header with the
list of additional recipients so that everyone else sees it;
<li> Adding a header <tt>Bcc</tt> is nonsense, unless it is
empty. Otherwise, everyone receiving the message will see it and that is
exactly what you <em>don't</em> want to happen!
</ul>
<p class=note>
I hope this clarifies the issue. Otherwise, please refer to
<a href="http://www.cs.princeton.edu/~diego/rfc/rfc2821.txt">RFC 2821</a>
and
<a href="http://www.cs.princeton.edu/~diego/rfc/rfc2822.txt">RFC 2822</a>.
</p>
<pre class=example>
-- load the smtp support
local smtp = require("smtp")
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-- Connects to server "localhost" and sends a message to users
-- "fulano@tecgraf.puc-rio.br", "beltrano@tecgraf.puc-rio.br",
-- and "sicrano@tecgraf.puc-rio.br".
-- Note that "fulano" is the primary recipient, "beltrano" receives a
-- carbon copy and neither of them knows that "sicrano" received a blind
-- carbon copy of the message.
from = "&lt;luasocket@tecgraf.puc-rio.br&gt;"
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rcpt = {
"&lt;fulano@tecgraf.puc-rio.br&gt;",
"&lt;beltrano@tecgraf.puc-rio.br&gt;",
"&lt;sicrano@tecgraf.puc-rio.br&gt;"
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}
mesgt = {
headers = {
to = "Fulano da Silva &lt;fulano@tecgraf.puc-rio.br&gt;",
cc = '"Beltrano F. Nunes" &lt;beltrano@tecgraf.puc-rio.br&gt;',
subject = "My first message"
}
body = "I hope this works. If it does, I can send you another 1000 copies."
}
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r, e = smtp.send{
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from = from,
rcpt = rcpt,
source = smtp.message(mesgt)
}
</pre>
<!-- message ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
<p class=name id=message>
smtp.<b>message(</b>mesgt<b>)</b>
</p>
<p class=description>
Returns a LTN12 source that sends an SMTP message body, possibly multipart
(arbitrarily deep).
</p>
<p class=parameters>
The only parameter of the function is a table describing the message.
<tt>Mesgt</tt> has the following form (notice the recursive structure):
</p>
<blockquote>
<table summary="Mesgt table structure">
<tr><td><tt>
mesgt = {<br>
&nbsp;&nbsp;headers = <i>header-table</i>,<br>
&nbsp;&nbsp;body = <i>LTN12 source</i> or <i>string</i> or
<i>multipart-mesgt</i><br>
}<br>
&nbsp;<br>
multipart-mesgt = {<br>
&nbsp;&nbsp;preamble = <i>string</i><br>
&nbsp;&nbsp;[1] = <i>mesgt</i>,<br>
&nbsp;&nbsp;[2] = <i>mesgt</i>,<br>
&nbsp;&nbsp;...<br>
&nbsp;&nbsp;[<i>n</i>] = <i>mesgt</i>,<br>
&nbsp;&nbsp;epilogue = <i>string</i>,<br>
}<br>
</tt></td></tr>
</table>
</blockquote>
<p class=parameters>
For a simple message, all that is needed is a set of <tt>headers</tt>
and the <tt>body</tt>. The message <tt>body</tt> can be given as a string
or as a LTN12 source. For multipart messages, the body is a table that
recursively defines each part as an independent message, plus a preamble
and an epilogue.
</p>
<p class=return>
The function returns an LTN12 source that produces the message contents as
defined by <tt>mesgt</tt>. Hopefuly, the following example will make
things clear. When in doubt, refer to the appropriate RFC as listed in the
introduction. </p>
<pre class=example>
-- load the smtp support and its friends
local smtp = require("smtp")
local mime = require("mime")
local ltn12 = require("ltn12")
-- creates a source to send a message with two parts. The first part is
-- plain text, the second part is a PNG image, encoded as base64.
source = smtp.message{
headers = {
-- Remember that headers are *ignored* by smtp.send.
from = "Sicrano de Oliveira &lt;sicrano@tecgraf.puc-rio.br&gt;",
to = "Fulano da Silva &lt;fulano@tecgraf.puc-rio.br&gt;",
subject = "Here is a message with attachments"
},
body = {
preamble = "If your client doesn't understand attachments, \r\n" ..
"it will still display the preamble and the epilogue.\r\n",
"Preamble might show up even in a MIME enabled client.",
-- first part: no headers means plain text, us-ascii.
-- The mime.eol low-level filter normalizes end-of-line markers.
[1] = {
body = mime.eol(0, [[
Lines in a message body should always end with CRLF.
The smtp module will *NOT* perform translation. It will
perform necessary stuffing or '.' characters, though.
]])
},
-- second part: headers describe content to be a png image,
-- sent under the base64 transfer content encoding.
-- notice that nothing happens until the message is actually sent.
-- small chunks are loaded into memory right before transmission and
-- translation happens on the fly.
[2] = {
headers = {
["content-type"] = 'image/png; name="image.png"',
["content-disposition"] = 'attachment; filename="image.png"',
["content-description"] = 'a beautiful image',
["content-transfer-encoding"] = "BASE64"
},
body = ltn12.source.chain(
ltn12.source.file(io.open("image.png", "rb")),
ltn12.filter.chain(
mime.encode("base64"),
mime.wrap()
)
)
},
epilogue = "This might also show up, but after the attachments"
}
}
-- finally send it
r, e = smtp.send{
from = "&lt;sicrano@tecgraf.puc-rio.br&gt;",
rcpt = "&lt;fulano@tecgraf.puc-rio.br&gt;",
source = source,
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}
</pre>
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<small>
Last modified by Diego Nehab on <br>
Sat Aug 9 01:00:41 PDT 2003
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