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Multiplayer protocol: Difference between revisions
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== Data types == | == Data types == | ||
{{Warning|if an aircraft defines all possible properties in the protocol, it tries to send 14988 bytes per packet, almost 12.5 times the allowed limit | {{Warning|if an aircraft defines all possible properties in the protocol, it tries to send 14988 bytes per packet, almost 12.5 times the allowed limit. Until the protocol is fixed to handle this it is the responsibility of the aircraft modeler to resolve '''Multiplayer packet truncated''' errors. <ref>{{cite web | ||
|url = https://sourceforge.net/p/flightgear/mailman/message/35441502/ | |url = https://sourceforge.net/p/flightgear/mailman/message/35441502/ | ||
|title = <nowiki> Re: [Flightgear-devel] C172 MP alert on console </nowiki> | |title = <nowiki> Re: [Flightgear-devel] C172 MP alert on console </nowiki> | ||
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}}</ref> | }}</ref> | ||
}} | }} | ||
{{Caution| | {{Caution|Prior to V2017.2 all bytes in the <tt>STRING</tt> field are sent as '''4-byte ints''' (not in the header or the position message). So STR has length (LEN * 4) bytes and padding ((4 - LEN%4) * 4) bytes, if LEN%4 is not 0.}} | ||
When running with 2017.2 there is a '''Transmit As''' mapping to allow more efficient usage of the limited space in the packet. This mapping is defined in the property map. | |||
The data is XDR encoded in two different methods, compatible or 2017.2. This only affects the properties, with the impact that clients prior to 2017.2 will only be able to receive properties using compatible encoding, which can result in missing animations and no receipt of chat messages. | |||
=== Compatible encoding === | |||
Prior to 2017.2 the following types are available. | |||
{| class="wikitable" | {| class="wikitable" | ||
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PAD: (n * 4) bytes, padding<br/> | PAD: (n * 4) bytes, padding<br/> | ||
|} | |} | ||
=== 2017.2 encoding === | |||
All properties are transmitted unconditionally in each frame at the rate specified. | |||
{| class="wikitable" | |||
! Type !! Size !! Remarks | |||
|- | |||
| int | |||
| 4 bytes | |||
|- | |||
| short int | |||
| 2 bytes | |||
|- | |||
| float | |||
| 4 bytes | |||
|- | |||
| Short_float_norm | |||
| 2 bytes | |||
| -1 .. 1 encoded into a short int | |||
|- | |||
| Short_float_1 | |||
| 2 bytes | |||
| range -3276.7 .. 3276.7 float encoded into a short int (16 bit) | |||
|- | |||
| Short_float_2 | |||
| 2 bytes | |||
| range -327.67 .. 327.67 float encoded into a short int (16 bit) | |||
|- | |||
| Short_float_3 | |||
| 2 bytes | |||
| range -32.767 .. 32.767 float encoded into a short int (16 bit) | |||
|- | |||
| Short_float_4 | |||
| 2 bytes | |||
| range -3.2767 .. 3.2767 float encoded into a short int (16 bit) | |||
|- | |||
| bool | |||
| 4 bytes | |||
|- | |||
| string | |||
| (LEN + STR) bytes | |||
| | |||
LEN: 2 bytes, length of the string<br/> | |||
STR: char[LEN] bytes<br/> | |||
|} | |||
Also with 2017.2 the property ID for short int and strings is transmitted in 16bits. | |||
== Messages == | == Messages == | ||