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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<th colspan="3" align="center">LPRng-HOWTO: 1 Apr 2002
(For LPRng-3.8.10)</th>
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<td width="80%" align="center" valign="bottom">Chapter
19. RFC 1179 - Line Printer Daemon Protocol</td>
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<div class="SECT1">
<h1 class="SECT1"><a name="REMOTESUPPORT">19.2. Protocol
Requests and Replies</a></h1>
<p>Options used:</p>
<ul>
<li>
<p><tt class="LITERAL">remote_support=</tt><i class=
"EMPHASIS">Remote operations supported</i></p>
</li>
</ul>
<br>
<br>
<p>After a connection has been established, a request can be
sent to the <b class="APPLICATION">lpd</b> server. The
request consists of a single octet indicating the request
type, followed by the printer (or print queue) name, followed
by a set of options for the request, followed by a LF (line
feed) character.</p>
<div class="TABLE">
<a name="RF1179COMMANDS"></a>
<p><b>Table 19-1. RFC1179 Commands</b></p>
<table border="1" class="CALSTABLE">
<thead>
<tr>
<th align="LEFT" valign="TOP">NNN</th>
<th align="LEFT" valign="TOP">RFC1179</th>
<th align="LEFT" valign="TOP">Operation</th>
<th align="LEFT" valign="TOP">program</th>
</tr>
</thead>
<tbody>
<tr>
<td align="LEFT" valign="TOP">1</td>
<td align="LEFT" valign="TOP">yes</td>
<td align="LEFT" valign="TOP">start print</td>
<td align="LEFT" valign="TOP"><b class=
"APPLICATION">lpc</b></td>
</tr>
<tr>
<td align="LEFT" valign="TOP">2</td>
<td align="LEFT" valign="TOP">yes</td>
<td align="LEFT" valign="TOP">transfer a printer
job</td>
<td align="LEFT" valign="TOP"><b class=
"APPLICATION">lpr</b></td>
</tr>
<tr>
<td align="LEFT" valign="TOP">3</td>
<td align="LEFT" valign="TOP">yes</td>
<td align="LEFT" valign="TOP">print short form of
queue status</td>
<td align="LEFT" valign="TOP"><b class=
"APPLICATION">lpr</b></td>
</tr>
<tr>
<td align="LEFT" valign="TOP">4</td>
<td align="LEFT" valign="TOP">yes</td>
<td align="LEFT" valign="TOP">print long form of
queue status</td>
<td align="LEFT" valign="TOP"><b class=
"APPLICATION">lpr</b></td>
</tr>
<tr>
<td align="LEFT" valign="TOP">5</td>
<td align="LEFT" valign="TOP">yes</td>
<td align="LEFT" valign="TOP">remove jobs</td>
<td align="LEFT" valign="TOP"><b class=
"APPLICATION">lprm</b></td>
</tr>
<tr>
<td align="LEFT" valign="TOP">6</td>
<td align="LEFT" valign="TOP"><b class=
"APPLICATION">LPRng</b></td>
<td align="LEFT" valign="TOP">do control
operation</td>
<td align="LEFT" valign="TOP"><b class=
"APPLICATION">lpc</b></td>
</tr>
<tr>
<td align="LEFT" valign="TOP">7</td>
<td align="LEFT" valign="TOP"><b class=
"APPLICATION">LPRng</b></td>
<td align="LEFT" valign="TOP">transfer a block format
print job</td>
<td align="LEFT" valign="TOP"><b class=
"APPLICATION">lpr</b></td>
</tr>
<tr>
<td align="LEFT" valign="TOP">8</td>
<td align="LEFT" valign="TOP"><b class=
"APPLICATION">LPRng</b></td>
<td align="LEFT" valign="TOP">secure command
transfer</td>
<td align="LEFT" valign="TOP"><b class=
"APPLICATION">lpc</b></td>
</tr>
<tr>
<td align="LEFT" valign="TOP">9</td>
<td align="LEFT" valign="TOP"><b class=
"APPLICATION">LPRng</b></td>
<td align="LEFT" valign="TOP">verbose status
information</td>
<td align="LEFT" valign="TOP"><b class=
"APPLICATION">lpr</b></td>
</tr>
</tbody>
</table>
</div>
<p>After the request has been sent, then a reply will be
returned. In general the reply has the following form:</p>
<div class="INFORMALEXAMPLE">
<a name="AEN9839"></a>
<pre class="SCREEN">
\000\n Success
\NNN\n Failure (NNN is error code)
text\n Text or status information
</pre>
</div>
<br>
<br>
<p>As can be seen, this protocol is extremely simple, but
there are a set of problems due to the loosely written
language of RFC1179.</p>
<ol type="1">
<li>
<p>Firstly, while RFC1179 sets limits on the lengths of
commands, it does not strictly set limits on the
characters set used in the commands. This can result in
problems when trying to print status information, headers
on banners, and other details.</p>
</li>
<li>
<p>The original RFC1179 protocol did not provide any way
to do remote control of queues or <b class=
"APPLICATION">lpd</b> servers. This has been added to the
protocol. As a side effect, if you try to use <b class=
"APPLICATION">lpc</b> to control a non-<b class=
"APPLICATION">LPRng</b> printer, it will not work.</p>
</li>
<li>
<p>You can specify that a network printer is non-<b
class="APPLICATION">LPRng</b> by using the <tt class=
"LITERAL">remote_support=RQVMC</tt> option and specify
the operations supported by the printer. The letters R,
Q, M, and C stand for <b class="APPLICATION">lpr</b>, <b
class="APPLICATION">lpq</b>, <b class=
"APPLICATION">lprm</b>, and <b class=
"APPLICATION">lpc</b> operations respectively, and
indicate that these are supported. If <tt class=
"LITERAL">remote_support</tt> does not allow a particular
operation, then the <b class="APPLICATION">LPRng</b>
software will not send a corresponding request to the
printer. For example, <tt class=
"LITERAL">remote_support=R</tt> would restrict operations
to spooling jobs only, and the <b class=
"APPLICATION">LPRng</b> software would not query the
printer for status.</p>
</li>
</ol>
<br>
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