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The TCP/IP Guide
9 TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
9 TCP/IP Key Applications and Application Protocols
9 TCP/IP File and Message Transfer Applications and Protocols (FTP, TFTP, Electronic Mail, USENET, HTTP/WWW, Gopher)
9 TCP/IP Electronic Mail System: Concepts and Protocols (RFC 822, MIME, SMTP, POP3, IMAP)
9 TCP/IP Electronic Mail Message Formats and Message Processing: RFC 822 and MIME
9 TCP/IP Enhanced Electronic Mail Message Format: Multipurpose Internet Mail Extensions (MIME)
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MIME Composite Media Types: Multipart and Encapsulated Message Structures
(Page 5 of 6)
Example Multipart Message
Table 248
contains a specific example of a multipart message (with portions abbreviated
to keep length down), so you can see what one looks like in text form.
(If you want to see more, you probably have several in your own e-mail
inbox right now!)
Table 248: Example MIME Multipart Message
From: Joe
Sender <joe@someplace.org>
To: Jane Receiver <jane@somewhereelse.com>
Date: Sun, 1 Jun 2003 13:28:19 0800
Subject: Photo and discussion
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="exampledelimtext123"
This is a multipart message in MIME format
exampledelimtext123
Content-Type: text/plain
Jane, here is the photo you wanted me for the new client.
Here are some notes on how it was processed.
(Blah blah blah
)
Talk to you soon,
Joe.
exampledelimtext123
Content-Type: image/jpeg; name="clientphoto.jpg"
Content-Transfer-Encoding: base64
SDc9Pjv/2wBDAQoLCw4NDhwQEBw7KCIoOzs7Ozs7Ozs
zv/wAARCADIARoDASIAAhEBAxEB/8QAHAAAAQUBA
exampledelimtext123
(Epilogue)
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In this example, Joe is
sending Jane a multipart message containing a JPEG photograph and some
explanatory text. The main header of the message specifies the multipart/mixed
type and a boundary string of exampledelimtext123. The message
begins with the preamble, which is ignored by the recipient e-mail
client but can be seen by the human reader. It is common to put a string
here such as the one given in this example. That way, if a person using
a client that does not support MIME receives the message, the recipient
will know what it is.
The first delimiter string is then
placed in the message, followed by the first body part, the text Joe
is sending Jane. This is preceded by whatever headers are needed by
the body part, in this case Content-Type:
text/plain. (Note, however, that this
is the default in MIME, so it could be omitted here.) After the text
message is another delimiter and then the encoded JPEG photo in the
second body part, with its own headers. Finally, one more delimiter
and then a space for the epilogue. This is ignored if present,
and is often not used at all.
It is possible to send a multipart
message that has only a single body part. This is sometimes done to
take advantage of the preamble area to provide information about how
to decode a non-text media type. Of course, this can also be done by
including such text decoding instructions as a body part.
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Version 3.0 - Version Date: September 20, 2005
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