<html lang="en">
<head>
<title>Notification Packets - Debugging with GDB</title>
<meta http-equiv="Content-Type" content="text/html">
<meta name="description" content="Debugging with GDB">
<meta name="generator" content="makeinfo 4.13">
<link title="Top" rel="start" href="index.html#Top">
<link rel="up" href="Remote-Protocol.html#Remote-Protocol" title="Remote Protocol">
<link rel="prev" href="Interrupts.html#Interrupts" title="Interrupts">
<link rel="next" href="Remote-Non_002dStop.html#Remote-Non_002dStop" title="Remote Non-Stop">
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
<!--
Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being ``Free Software'' and ``Free Software Needs
Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
and with the Back-Cover Texts as in (a) below.

(a) The FSF's Back-Cover Text is: ``You are free to copy and modify
this GNU Manual.  Buying copies from GNU Press supports the FSF in
developing GNU and promoting software freedom.''-->
<meta http-equiv="Content-Style-Type" content="text/css">
<style type="text/css"><!--
  pre.display { font-family:inherit }
  pre.format  { font-family:inherit }
  pre.smalldisplay { font-family:inherit; font-size:smaller }
  pre.smallformat  { font-family:inherit; font-size:smaller }
  pre.smallexample { font-size:smaller }
  pre.smalllisp    { font-size:smaller }
  span.sc    { font-variant:small-caps }
  span.roman { font-family:serif; font-weight:normal; } 
  span.sansserif { font-family:sans-serif; font-weight:normal; } 
--></style>
<link rel="stylesheet" type="text/css" href="../cs.css">
</head>
<body>
<div class="node">
<a name="Notification-Packets"></a>
<p>
Next:&nbsp;<a rel="next" accesskey="n" href="Remote-Non_002dStop.html#Remote-Non_002dStop">Remote Non-Stop</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="Interrupts.html#Interrupts">Interrupts</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="Remote-Protocol.html#Remote-Protocol">Remote Protocol</a>
<hr>
</div>

<h3 class="section">D.10 Notification Packets</h3>

<p><a name="index-notification-packets-2490"></a><a name="index-packets_002c-notification-2491"></a>
The <span class="sc">gdb</span> remote serial protocol includes <dfn>notifications</dfn>,
packets that require no acknowledgment.  Both the GDB and the stub
may send notifications (although the only notifications defined at
present are sent by the stub).  Notifications carry information
without incurring the round-trip latency of an acknowledgment, and so
are useful for low-impact communications where occasional packet loss
is not a problem.

   <p>A notification packet has the form &lsquo;<samp><span class="samp">% </span><var>data</var><span class="samp"> #
</span><var>checksum</var></samp>&rsquo;, where <var>data</var> is the content of the notification,
and <var>checksum</var> is a checksum of <var>data</var>, computed and formatted
as for ordinary <span class="sc">gdb</span> packets.  A notification's <var>data</var>
never contains &lsquo;<samp><span class="samp">$</span></samp>&rsquo;, &lsquo;<samp><span class="samp">%</span></samp>&rsquo; or &lsquo;<samp><span class="samp">#</span></samp>&rsquo; characters.  Upon
receiving a notification, the recipient sends no &lsquo;<samp><span class="samp">+</span></samp>&rsquo; or &lsquo;<samp><span class="samp">-</span></samp>&rsquo;
to acknowledge the notification's receipt or to report its corruption.

   <p>Every notification's <var>data</var> begins with a name, which contains no
colon characters, followed by a colon character.

   <p>Recipients should silently ignore corrupted notifications and
notifications they do not understand.  Recipients should restart
timeout periods on receipt of a well-formed notification, whether or
not they understand it.

   <p>Senders should only send the notifications described here when this
protocol description specifies that they are permitted.  In the
future, we may extend the protocol to permit existing notifications in
new contexts; this rule helps older senders avoid confusing newer
recipients.

   <p>(Older versions of <span class="sc">gdb</span> ignore bytes received until they see
the &lsquo;<samp><span class="samp">$</span></samp>&rsquo; byte that begins an ordinary packet, so new stubs may
transmit notifications without fear of confusing older clients.  There
are no notifications defined for <span class="sc">gdb</span> to send at the moment, but we
assume that most older stubs would ignore them, as well.)

   <p>The following notification packets from the stub to <span class="sc">gdb</span> are
defined:

     <dl>
<dt>&lsquo;<samp><span class="samp">Stop: </span><var>reply</var></samp>&rsquo;<dd>Report an asynchronous stop event in non-stop mode. 
The <var>reply</var> has the form of a stop reply, as
described in <a href="Stop-Reply-Packets.html#Stop-Reply-Packets">Stop Reply Packets</a>.  Refer to <a href="Remote-Non_002dStop.html#Remote-Non_002dStop">Remote Non-Stop</a>,
for information on how these notifications are acknowledged by
<span class="sc">gdb</span>. 
</dl>

   </body></html>