134 lines
3.8 KiB
HTML
134 lines
3.8 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<!-- SMTP.html (C) K. J. Turner 18/12/14 -->
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<title>Simple Mail Transfer Protocol</title>
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<link rev="made" href="http://www.cs.stir.ac.uk/~kjt/"/>
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</head>
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<body background="simulator.jpeg">
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<div style="text-align: center">
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<h1>Simple Mail Transfer Protocol Simulator</h1>
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<img src="simulator.gif" alt="Simulator Logo"/>
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</div>
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<h2>Protocol Description</h2>
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<p>
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SMTP (Simple Mail Transfer Protocol) is used to transfer email messages.
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SMTP operates over <a href="TCPcs.html">TCP (Transmission Control
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Protocol)</a> in client-server mode for reliable transfer of data. The
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protocol simulation deals with the main commands (sent in approximately
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the order below):
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</p>
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<ul>
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<li><em>HELO</em>: names the client (the spelling is deliberate)</li>
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<li><em>MAIL FROM</em>: names the sender</li>
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<li><em>RCPT TO</em>: names a recipient</li>
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<li><em>DATA</em>: asks to send message data</li>
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<li>c<em>Mail Message</em>: sends the message datac</li>
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<li>c<em>QUIT</em>: finishes the mail sessionc</li>
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</ul>
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<p>
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The simulation supports a limited range of response codes:
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</p>
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<ul>
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<li>
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<em>220 Server ready</em>: a connection to the server has been made and
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the server is ready
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</li>
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<li>
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<em>221 Server closing</em>: the server accepted the <em>QUIT</em>
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command and is ready to close the connection
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</li>
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<li>
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<em>250 OK</em>: the server accepted the command (one of several
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similar responses)
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</li>
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<li>
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<em>354 Send mail</em>: the server accepted the <em>DATA</em> command
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and is waiting for the <em>Mail Message</em>
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</li>
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<li>
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<em>550 Invalid</em>: the server rejected the command (one of several
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similar responses)
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</li>
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</ul>
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<p>
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After the client connects to the server using TCP, the server reports its
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readiness with a <em>220 Server ready</em> response. The client names
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itself in <em>HELO</em>, to which the server normally gives a <em>250
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Server hello to client</em> response. To send mail, the client issues
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<em>MAIL FROM</em> and normally gets a <em>250 Sender OK</em> response.
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Recipients are named in <em>RCPT TO</em>, normally obtaining <em>250
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Recipient OK</em> responses. However the server can reject a sender or
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recipient with a <em>550 Sender invalid</em> or <em>550 Recipient
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invalid</em> response. Once all parties have been named, the client sends
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<em>DATA</em> to begin message transmission; a <em>354 Send mail</em>
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response is expected from the server. At this point, the real protocol
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would send the lines of the message followed by a full stop. In the
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simulation, a single <em>Mail Message</em> command stands for this. The
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server will normally give a <em>250 Message accepted</em> response and
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further messages can be sent. Finally, the client sends <em>QUIT</em> and
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the server responds with a <em>221 Server closing</em> code. At this
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point the TCP connection is broken.
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</p>
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<h2>Protocol Parameters</h2>
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<p>
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This simulation has no parameters.
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</p>
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<h2>Protocol Simulation</h2>
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<center>
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<applet code="simulator.ProtocolSimulator.class"
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archive="ProtocolSimulator.jar" width="600" height="700"
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name="ProtocolSimulator">
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<param name="protocol" value="SMTP"/>
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</applet>
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</center>
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<hr/>
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<p>
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<a href="index.html"><img src="uparrow.gif" alt="Up Arrow"/></a>
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Up one level to <a href="index.html">Protocol Simulators</a>
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</p>
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</body>
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</html>
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