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+ <title>DXSpider Protocol</title>
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+ content="DX Cluster, DXSpider, Spider, Packet Cluster, DXCluster, Pavillion Software, AK1A, AX25, AX.25, WWV, Packet Radio, Amateur Radio, Propagation, DX, DXing, G1TLH, GB7TLH, Dirk Koopman, Mailing list, Linux, RedHat, PERL">
+ <meta name="Description"
+ content="Software and systems for realtime digital communications between amateur radio stations for the provision of information on propagation conditions and stations operating">
+ <meta name="Author" content="Dirk Koopman G1TLH">
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+
+<h2>DXSpider Protocol</h2>
+<hr>
+<address>
+ <a href="mailto:djk@tobit.co.uk">Dirk Koopman G1TLH</a>
+</address>
+<!-- standard footer -->
+
+
+<h3>Introduction</h3>
+
+<p><br>
+For some time now it has become obvious that the original AK1A protocol has
+become stretched to beyond breaking point. Some attempts have been made to
+extend it, but none have done what is actually required: which is to throw it
+away completely and start from scratch.</p>
+
+<p>This is an attempt at starting again.</p>
+
+<h3>Design Criteria</h3>
+<ul>
+ <li>The protocol shall be open, published and available for any author to
+ use.</li>
+ <li>The protocol shall versioned, to allow easy upgrade.</li>
+ <li>The protocol shall be layered to allow the use of different transport
+ mechanisms (eg: radio, UDP, TCP, multicast).</li>
+ <li>Sentences in the protocol shall be capable of being verified as being
+ unaltered.</li>
+ <li>all sentences shall have an originating node, a serial number and a
+ destination. These fields must not be altered by intermediate nodes.</li>
+ <li>all sentences shall have similar fields in the same order.</li>
+ <li>sentences shall be in latin-1 and must not contain any characters other
+ than those between 0x20 and 0x7e. Any characters outside of this range
+ will be HTML escaped (viz: converted into the form '%', hex digit, hex
+ digit; eg: carriage return (0x0d) is converted to '%0D').</li>
+ <li>There shall be a mechanism for verifying "sensitive" information and/or
+ connections.</li>
+</ul>
+
+<h3>Definitions</h3>
+<dl>
+ <dt><callsign></dt>
+ <dd>A callsign can contain the characters [0-9A-Z\-/]. It is always in
+ upper case.</dd>
+ <dt><nodecall></dt>
+ <dd>A callsign of a node. It can contain the same characters as a
+ <callsign></dd>
+ <dt><origin></dt>
+ <dd>The callsign of the originating node, it is a <nodecall>.</dd>
+ <dt><destination></dt>
+ <dd>The callsign of the destination node, this could be a
+ <nodecall> or empty (which implies that this is a broadcast).</dd>
+ <dt><touser></dt>
+ <dd>The callsign of a user to which this sentence is directed. It is a
+ <callsign> or empty.</dd>
+ <dt><fromuser></dt>
+ <dd><p>The callsign of the user from which this sentence originally come
+ came from. It is a <callsign>.</p>
+ </dd>
+ <dt><serial></dt>
+ <dd>The serial number of this sentence. It is a number between 0 and
+ 9999.</dd>
+ <dt><time></dt>
+ <dd>A time in standard 'time_t' format, the number of seconds since 00:00
+ 1st Jan 1970 (the 'epoch'), the output of the standard system 'time()'
+ subroutine call in both unix and MS-Dos/Windows.</dd>
+ <dt><minutes></dt>
+ <dd>The number of minutes since the epoch. This is actually <time>
+ / 60 with no remainder.</dd>
+ <dt><flags></dt>
+ <dd>A bit field containing various binary values.</dd>
+ <dt><digit></dt>
+ <dd>A character, representing a numeral, befween '0' and '9'.</dd>
+ <dt><hex digit></dt>
+ <dd>A character, representing a hexadecimal numeral (a value between
+ 0->15 [a nibble]), '0'->'9' and 'A'->'F'.</dd>
+ <dt><field></dt>
+ <dd>A part of a protocol sentence.</dd>
+ <dt><freq></dt>
+ <dd>A frequency, in kilohertz with an optional (single digit) decimal
+ part (ie both 14001 and 14325.1 are valid).</dd>
+ <dt><text></dt>
+ <dd>Some text in ISO-Latin-1 in both upper and lower case.</dd>
+ <dt><cs></dt>
+ <dd>A checksum of two <hex digits></dd>
+ <dt><cr></dt>
+ <dd>A carriage return character (0x0d)</dd>
+ <dt><lf></dt>
+ <dd>A line feed character (0x0a)</dd>
+</dl>
+
+<p></p>
+
+<h3>The Protocol</h3>
+
+<p></p>
+
+<p>Each protocol line is separate and distinct. This is a "datagram" style
+protocol. Each protocol line is called a "sentence" and begins with the
+string "DX" in upper case, followed by two digits. The sentence is terminated
+by a <cr> or a <lf> character or both. Internally, the
+terminating characters should be discarded completely and the sentence
+processed without.</p>
+
+<p>The character set used shall be ISO-Latin-1, with only the characters 0x20
+-> 0x7e permitted within a sentence. All other characters shall be "HTML
+Escaped" which is that they shall be replaced by the three character scheme
+of '%', <hex digit>, <hex digit>.</p>
+
+<p>The sentence is split up into <fields> which are delimited by the
+'|' character (0x7c). If the '|' character occurs within a <field> it
+shall be replaced by the string '%7C'.</p>
+
+<p>There is no intrinsic maximum length of a sentence. Having said that,
+there will be some underlying maximum lengths implied by the transport
+mechanisms employed. Because one of those transport mechanisms is likely to
+be AX25 in UI mode. It is recommended that broadcast sentences shall be no
+more than 200 bytes in length.</p>
+
+<p>All sentences shall have a <checksum> in a separate <field> at
+the end. The checksum is simply the sum, modulo 256, of all the characters of
+the sentence except for the final <field> separator and the two <hex
+digits> of the checksum itself. The purpose of the checksum is to check
+that no intermediate node has changed the sentence. It is assumed that the
+underlying transport mechanisms will deal with communications errors.</p>
+
+<p>All sentences shall have an <origin>, a <destination> and a
+<serial> number. The <destination> can be empty which implies
+that this sentence is to be broadcast. The <serial> number is a global
+number, which is used for all sentences originating at a node, that is
+incremented modulo 10000, and is used to determine duplicate or out of date
+sentences.</p>
+
+<p>So the generic form of a sentence is:-</p>
+
+<p></p>
+
+<blockquote class="code">
+ DX99|<origin>|<destination>|<serial>|...|<cs></blockquote>
+
+<p></p>
+
+<p>Some examples:-</p>
+
+<blockquote>
+ <p class="code">DX01|GB7TLH||0|</p>
+</blockquote>
+
+<p></p>
+<hr>
+<span class="copy">Copyright © 2001 by Dirk Koopman G1TLH. All Rights
+Reserved</span>
+ <br>
+<span class="id">$Id: index.html,v 1.19 2001/04/17 20:44:11 g0vgs Exp
+$</span></body>
+</html>
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