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==GSNet Msg (Visual) Breakdown==
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[[Image:GSNetMsgBreakdown.png|520x373px]]
  
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=GSNet Msg Description=
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==GSNet Msg==
==Header==
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===Header===
The header of the GSNet Msg contains the information necessary for quickly determining authenticity, type and length.  Geometry Service's network library, libNetwork, has a header byte layout that looks like this:
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The header of the GSNet Msg contains the information necessary for quickly determining authenticity, type and length.  Geometry Service's network library, libNetwork, is built upon BRL-CAD's networking library: libPKG.  This causes the header byte layout to look like this:
 
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|style="border: 1px solid #666699; background-color: #666699; color: #FFFFFF; width: 180px;"|'''Value'''
 
|style="border: 1px solid #666699; background-color: #666699; color: #FFFFFF; width: 180px;"|'''Value'''
 
|-
 
|-
|style="border: 1px solid #666699;"|MsgType
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|style="border: 1px solid #666699;"|Magic1
|style="border: 1px solid #666699;"|int16 (2 bytes)
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|style="border: 1px solid #666699;"|int16 (2 Bytes)
|style="border: 1px solid #666699;"|
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|style="border: 1px solid #666699;"|Always 0x41FE
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|-
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|style="border: 1px solid #666699;"|Magic2
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|style="border: 1px solid #666699;"|int16 (2 Bytes)
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|style="border: 1px solid #666699;"|Always 0x5309
 
|-
 
|-
 
|style="border: 1px solid #666699;"|MessageLength
 
|style="border: 1px solid #666699;"|MessageLength
 
|style="border: 1px solid #666699;"|int32 (4 bytes)
 
|style="border: 1px solid #666699;"|int32 (4 bytes)
|style="border: 1px solid #666699;"|Does *NOT* include the type or length, so is packet size - 6
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|style="border: 1px solid #666699;"|
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|-
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|style="border: 1px solid #666699;"|MsgType
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|style="border: 1px solid #666699;"|int16 (2 bytes)
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|style="border: 1px solid #666699;"|
 
|-
 
|-
 
|style="border: 1px solid #666699;"|MessageUUID
 
|style="border: 1px solid #666699;"|MessageUUID
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|}
 
|}
  
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====libPKG Part====
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Due to some C and C++ incompatibilities, the libPKG "Type" parameter is used as "Magic2" in the GSNet Protocol.  This is due to libPKG's need for each network connection to have a callback table that maps NetMsg types to pointers to the appropriate NetMsg handler function.  The GSNetwork library uses a publish/subscription scheme to route NetMsg.  LibPKG strips off the libPKG header before calling the appropriate callback function, thus making per class deserialization extremely complex.  To address these issues, the GSNetwork library routes NetMsg based on the "GS Msg Type" parameter rather than the "libPKG Type" parameter.
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<br /><br />
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Table showing modifications described above:
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<br /><br />
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{|style="border-collapse: separate; border-spacing: 0; border-width: 1px; border-style: solid; border-color: #666699; padding: 0;"
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|style="border: 1px solid #666699; background-color: #666699; color: #FFFFFF; width: 180px;"|'''libPKG element'''
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|style="border: 1px solid #666699; background-color: #666699; color: #FFFFFF; width: 180px;"|'''GSNet element'''
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|-
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|style="border: 1px solid #666699;"|Magic
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|style="border: 1px solid #666699;"|Magic01
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|-
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|style="border: 1px solid #666699;"|Type
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|style="border: 1px solid #666699;"|Magic02
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|-
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|style="border: 1px solid #666699;"|Length
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|style="border: 1px solid #666699;"|Length
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|}
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* '''Magic01:''' 2 bytes of data designed to ensure integrity of data and mark NetMsg starting point.
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* '''Magic02:''' 2 bytes of data designed to ensure integrity of data and mark NetMsg starting point.
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* '''Length:''' 4 byte integer that represents the number of bytes in the message from the end of this value to the end.
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<br /><br />
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====GSNet Part====
  
 
* '''MsgType:''' 2 byte integer value that tells what type of message this is.
 
* '''MsgType:''' 2 byte integer value that tells what type of message this is.
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==Data==
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===Data===
 
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The Data load of a NetMsg is, obivously, the important and unique part.  Data Loads can be as small as zero (in the case of a TypeOnlyMsg) or many kilobytes long.
 
  
Here is a list of [[NetMsgTypes|NetMsg types]] and here is a list of [[Common NetMsg Exchanges]].
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List of [[NetMsgTypes]].
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List of [[Common NetMsg Exchanges]]

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