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10 content="Software and systems for realtime digital communications between amateur radio stations for the provision of information on propagation conditions and stations operating">
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19 <h2>DXSpider Protocol</h2>
22 <a href="mailto:djk@tobit.co.uk">Dirk Koopman G1TLH</a>
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30 For some time now it has become obvious that the original AK1A protocol has
31 become stretched to beyond breaking point. Some attempts have been made to
32 extend it, but none have done what is actually required: which is to throw it
33 away completely and start from scratch.</p>
35 <p>This is an attempt at starting again.</p>
37 <h3>Design Criteria</h3>
39 <li>The protocol shall be open, published and available for any author to
41 <li>The protocol shall versioned, to allow easy upgrade.</li>
42 <li>The protocol shall be layered to allow the use of different transport
43 mechanisms (eg: radio, UDP, TCP, multicast).</li>
44 <li>Sentences in the protocol shall be capable of being verified as being
46 <li>all sentences shall have an originating node, a serial number and a
47 destination. These fields must not be altered by intermediate nodes.</li>
48 <li>all sentences shall have similar fields in the same order.</li>
49 <li>sentences shall be in latin-1 and must not contain any characters other
50 than those between 0x20 and 0x7e. Any characters outside of this range
51 will be HTML escaped (viz: converted into the form '%', hex digit, hex
52 digit; eg: carriage return (0x0d) is converted to '%0D').</li>
53 <li>There shall be a mechanism for verifying "sensitive" information and/or
59 <dt><callsign></dt>
60 <dd>A callsign can contain the characters [0-9A-Z\-/]. It is always in
62 <dt><nodecall></dt>
63 <dd>A callsign of a node. It can contain the same characters as a
65 <dt><origin></dt>
66 <dd>The callsign of the originating node, it is a <nodecall>.</dd>
67 <dt><destination></dt>
68 <dd>The callsign of the destination node, this could be a
69 <nodecall> or empty (which implies that this is a broadcast).</dd>
70 <dt><touser></dt>
71 <dd>The callsign of a user to which this sentence is directed. It is a
72 <callsign> or empty.</dd>
73 <dt><fromuser></dt>
74 <dd>The callsign of the user from which this sentence originally come
75 came from. It is a <callsign>.</dd>
76 <dt><serial></dt>
77 <dd>The serial number of this sentence. It is a number between 0 and
80 <dd>A time in standard 'time_t' format, the number of seconds since 00:00
81 1st Jan 1970 (the 'epoch'), the output of the standard system 'time()'
82 subroutine call in both unix and MS-Dos/Windows.</dd>
83 <dt><minutes></dt>
84 <dd>The number of minutes since the epoch. This is actually <time>
85 / 60 with no remainder.</dd>
86 <dt><flags></dt>
87 <dd>A bit field containing various binary values.</dd>
88 <dt><digit></dt>
89 <dd>A character, representing a numeral, befween '0' and '9'.</dd>
90 <dt><hex digit></dt>
91 <dd>A character, representing a hexadecimal numeral (a value between
92 0->15 [a nibble]), '0'->'9' and 'A'->'F'.</dd>
93 <dt><field></dt>
94 <dd>A part of a protocol sentence.</dd>
96 <dd>A frequency, in kilohertz with an optional (single digit) decimal
97 part (ie both 14001 and 14325.1 are valid).</dd>
99 <dd>Some text in ISO-Latin-1 in both upper and lower case.</dd>
101 <dd>A checksum of two <hex digits></dd>
103 <dd>A carriage return character (0x0d)</dd>
105 <dd>A line feed character (0x0a)</dd>
110 <h3>The Protocol</h3>
114 <p>Each protocol line is separate and distinct. This is a "datagram" style
115 protocol. Each protocol line is called a "sentence" and begins with the
116 string "DX" in upper case, followed by two digits. The sentence is terminated
117 by a <cr> or a <lf> character or both. Internally, the
118 terminating characters should be discarded completely and the sentence
119 processed without.</p>
121 <p>The character set used shall be ISO-Latin-1, with only the characters 0x20
122 -> 0x7e permitted within a sentence. All other characters shall be "HTML
123 Escaped" which is that they shall be replaced by the three character scheme
124 of '%', <hex digit>, <hex digit>.</p>
126 <p>The sentence is split up into <fields> which are delimited by the
127 '|' character (0x7c). If the '|' character occurs within a <field> it
128 shall be replaced by the string '%7C'.</p>
130 <p>There is no intrinsic maximum length of a sentence. Having said that,
131 there will be some underlying maximum lengths implied by the transport
132 mechanisms employed. Because one of those transport mechanisms is likely to
133 be AX25 in UI mode. It is recommended that broadcast sentences shall be no
134 more than 200 bytes in length.</p>
136 <p>All sentences shall have a <checksum> in a separate <field> at
137 the end. The checksum is simply the sum, modulo 256, of all the characters of
138 the sentence except for the final <field> separator and the two <hex
139 digits> of the checksum itself. The purpose of the checksum is to check
140 that no intermediate node has changed the sentence. It is assumed that the
141 underlying transport mechanisms will deal with communications errors.</p>
143 <p>All sentences shall have an <origin>, a <serial> and a
144 <destination> number. The <destination> can be empty which implies
145 that this sentence is to be broadcast. The <serial> number is a global
146 number, which is used for all sentences originating at a node, that is
147 incremented modulo 10000, and is used to determine duplicate or out of date
150 <p>So the generic form of a sentence is:-</p>
154 <blockquote class="code">
155 DX99|<origin>|<serial>|<destination>|...|<cs></blockquote>
159 <p>Some examples:-</p>
161 <blockquote class="code">
162 DX01|GB7TLH|0|GB7DJK|DXSpider 1.48/53.287|DE450A30|F4<br>
163 DX01|GB7DJK|345|GB7TLH|DXSpider 1.49/60.45|4532DA56|A1<br>
164 DX11|GB7TLH|1||G1TLH|FR0G|164563|14001.1|Easy|53<br>
165 DX10|GB7TLH|2||G1TLH|SYSOP|GB7TLH rebooting|4A<br>
166 DX02|GB7TLH|3|GB7MBC|1|98012349|5D<br>
167 DX02|GB7MBC|9356|GB7TLH|0|GB7DJK/0.76,GB7BAA/1.2|AE<br>
172 <span class="copy">Copyright © 2001 by Dirk Koopman G1TLH. All Rights
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