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        <th colspan="3" align="center">LPRng Reference Manual: 24
        Sep 2004 (For LPRng-3.8.28)</th>
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        <td width="80%" align="center" valign="bottom">Chapter 11.
        Printer Communication and Protocols</td>

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  <div class="SECT1">
    <h1 class="SECT1"><a name="SECSERIAL" id="SECSERIAL">11.12.
    Serial Printers</a></h1>

    <p>If your printer is attached by a serial line, then you may
    need to set the serial line characteristics before sending the
    job to the printer. Here are a set of guidelines to following
    when attaching a serial port printer to a serial line.</p>

    <p>1. Check to make sure that the line is not enabled for
    login. Logins are usually managed by the <b class=
    "APPLICATION">getty</b> (BSD) or <b class=
    "APPLICATION">ttymon</b> (Solaris, SystemV). Check your system
    documentation and make sure that these daemons are not managing
    the serial line.</p>

    <p>2. Check the permissions and ownership of the serial line.
    For the most easy testing, set the permissions to 0666
    (everybody can open for reading and writing). After you have
    made sure that you can send jobs to the printer, you might want
    to change the ownership of the serial line to the <b class=
    "APPLICATION">lpd</b> server and change the permissions to
    0600.</p>

    <p>3. Make sure that you can print a test file on the printer
    via the serial port. This may require setting the line
    characteristics and then sending a file to the printer. You
    should try to use 8 bit, no parity, with hardware flow control
    and no special character interpretation, and definitely no LF
    to CR/LF translation. The problem is that different versions of
    UNIX systems have different sets of stty(1) commands to do
    this. The following simple test script can help in this.</p>

    <div class="INFORMALEXAMPLE">
      <a name="AEN5332" id="AEN5332"></a>
      <pre class="SCREEN">
#!/bin/sh
# 9600, no echo, no CR
FLAGS= 9600 -raw -parenb cs8 crtscts
DEV= /dev/tty01
(stty $FLAGS; stty 1&gt;&amp;2; cat $1 ) &lt;$DEV &gt;$DEV
</pre>
    </div>

    <p>This shows using stty to set the flags, then to print the
    current settings, and then using cat a file to the output. If
    you attach a dumb terminal to the serial port, you can even use
    this script to ensure that input from the device is echoed to
    the output with the correct speed, parity, etc.</p>

    <p>Experience has shown that serially connected printers are
    the least reliable and lowest speed. Where possible, it is
    strongly recommended that they be attached to a <span class=
    "emphasis"><i class="EMPHASIS">network print box</i></span>
    which will provide a Socket API interface and handle the low
    level network to serial port protocol conversions.</p>
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