Transcript Introduction to Python - Kansas State University

Sending E-mail
Topic 4, Chapters 9, 10
Network Programming
Kansas State University at Salina
E-mail messages
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7-bit ASCII (128 characters)
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Works for English text only messages
Initial binary file solution – uuencode and uudecode
(uu = UNIX to UNIX)
Variable headers: ‘To’, ‘From’, ‘Subject’, ‘Date’ and
‘Message-ID’ are the normal minimum. Others are
allowed and may be added by servers that handle
the message.
MIME – 1992
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Multipurpose Internet Mail Extensions
Divide the message into parts
Each part has headers including the type of data, filename,
encoding used and data encoded to 7-bit ASCII
MIME advantages
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Multiple attachments
Content types
Styled text with different fonts and colors
Interactive multimedia
Multi-language support for non-Roman
languages like Japanese, Chinese, Arabic,
Hebrew, etc...
Building simple messages in Python
from email.MIMEText import MIMEText
from email import Utils
import smtplib
message = """Hello,
This is a test message.
-- Tim"""
msg = MIMEText( message )
msg[ 'To' ] = 'you@home'
msg[ 'From' ] = 'me@school'
msg[ 'Subject' ] = 'Testing Python e-mail'
msg[ 'Date' ] = Utils.formatdate(localtime = 1)
msg[ 'Message-ID' ] = Utils.make_msgid()
server = 'localhost:8025'
s = smtplib.SMTP( server )
s.sendmail( msg['From'], [msg['To']], msg.as_string() )
s.close()
Multipart MIME messages
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Start with MIMEMultipart() object
Create MIMEText() objects for body and any
text attachments; attach to the message
For binary file attachments, create other
MIME objects, encode the data for each;
attach to the message.
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MIMEBase() – generic binary file
MIMEAudio() – audio file
MIMEImage() – graphic image file
See example code in book and posted on KState Online.
MIME Encoders
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encode_quopri
Encodes the payload into quoted-printable form and
sets the Content-Transfer-Encoding: header to quotedprintable7.2. This is a good encoding to use when
most of your payload is normal printable data, but
contains a few unprintable characters.
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encode_base64
Encodes the payload into base64 form and sets the
Content-Transfer Encoding: header to base64. This is
a good encoding to use when most of your payload is
unprintable data since it is a more compact form than
quoted-printable. The drawback of base64 encoding is
that it renders the text non-human readable.
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encode_7or8bit
This doesn't actually modify the message's payload,
but it does set the Content-Transfer-Encoding: header
to either 7bit or 8bit as appropriate, based on the
payload data.
MIME Alternatives
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Like MIMEMultipart, except the e-mail is to
display either one part or the other (text or
HTML). Multiple parts are to hold the same
content.
No Content-Disposition header is
inserted
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Content-Disposition header is used to give
the reader program some clues of what to do with
the file, such as a default file name for saving it.
Mime Alternatives are for viewing, so file handling
is not needed.
Parsing E-mail messages
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You may skip this part
More concerned with sending messages,
which is more common for non-interactive
programs to do than retrieving and parsing
messages.
SMTP
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Simple Mail Transport Protocol
Unlike HTTP, SMTP is a connection oriented
protocol
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Multiple messages exchanged between client and
server to set who the message is to and from and
to send the data.
Normal conversation is:
HELO domain_name
MAIL From: address
RCPT To: address1, address2,…
DATA
-- Send the message as a string –
Blank line followed by single period to indicate end of data
QUIT
SMTP (continued)
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See SMTPSocket.py – demonstration of simple
SMTP messages between client and server.
See demo video of running SMTPSocket.py
smtplib – very easy sending of e-mail
Always send data as a string
msg = MIMEText( message )
msg[ 'To' ] = 'you@home'
msg[ 'From' ] = 'me@school'
msg[ 'Subject' ] = 'Testing Python e-mail'
msg[ 'Date' ] = Utils.formatdate(localtime = 1)
msg[ 'Message-ID' ] = Utils.make_msgid()
s = smtplib.SMTP( 'localhost:8025‘ )
s.sendmail( msg['From'], [msg['To']], msg.as_string() )
s.close()
Fake mail Server
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Fakemail.py – Download it from K-State
Online
Found with package index on python.org
Creates a SMTP server that you can send
messages to for testing – much better for
debugging than sending to a real server.
Recommend to run from Command Prompt
python fakemail.py
Fake mail server (continued)
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Use cntrl-Break to stop the fakemail server.
Be patient, Windows is very slow to send
signals to processes. It is immediate in Unix.
Microsoft has never been able to implement
signals correctly.
Listens on port 8025 (Real SMTP port is 25)
Saves messages to files in same directory
Change file name extension to ‘eml’ to easily
view the message with your e-mail client.
ESMTP
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Extended Simple Mail Transfer Protocol
Newer version of SMTP
Supported by some servers
Allows clients to get information, such as
maximum allowed message size, from the
server prior to sending the message
Allows for encryption of the message
Allows for a login before accepting the
message
Protocol session begins with ‘EHLO’ instead
of ‘HELO’, which can be used to test if the
server uses ESMTP or SMTP