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From: Heiko Wengler <hw@plato.Chemietechnik.Uni-Dortmund.DE>
Message-Id: <9306070746.AA04496@plato.Chemietechnik.Uni-Dortmund.DE>
Subject: README for SHORT_PACKETS
To: short@plato.chemietechnik.uni-dortmund.de
Date: Mon, 7 Jun 1993 09:46:41 +0200 (MET DST)
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Short Packets Code by Tedd Hadley and Heiko Wengler.
Extra feature: ',' puts up a menu ('network' for your .xtrekrc) with
1 toggle options and 1 integer entry field:
and two new keys: '-' updateSmall 'xx' (not assigned yet) updateMiddle (:-)
'UpdateSmall' gives you an update of all weapons+Planets+Kills. ( <400 bytes)
'UpdateMiddle' is updateAll without the Stats. (< 700 bytes)
UpdateAll (<2200 bytes)
orig UpdateAll (4192 bytes)
MENU:
[Don't] Receive variable and short packets (1)
Receive threshold: (2)
Done
(1) Variable and short packets. This tells the server to send several
new types of packets instead of the original types. The technical
details follow at the end.
(2) Receive threshold. This is complete experimental. If a non-zero
threshold is specified the server tries to not overload the
connection.
This option could be not implemented in the server.
You should give as a threshold the number of bytes per second
you wanna give from your bandwith.
For example if you set the threshold to 500 bytes. And you are
playing with 5 updates/sec. You have a threshold of
500/updates = 100bytes/update. The server checks after every update
if he wrote more than the limit. If yes the server skips your
next update and you get a warning from your client.
This can actually halve your Updates/sec. Not more. (Eg if you
play with 5 updates it 'slows' you down to 3 updates.)
Minimum limit per update is 60 bytes. (Threshold = 60 * updates then.)
If you set it to 0 Server ends testing.
( If you wanna calculate your bandwith requirements you should count
the tcp/ip overhead of 64 bytes to the actual data. For example
if you wanna play with a 9600 Baud modem. You have a bandwith
of 1200 bytes. you can subtract 200 bytes for client-server
communication. So you have 1000 bytes to play with. With 5 updates
you need under tcp/ip (5*64=)320 bytes for headers.
You have then ~650 bytes for serverdata. That means you should
set the threshold to 650 bytes. ( 130 bytes per update are much.
All playermovement(16 players) +SP_S_YOU + 16 Torps.) I do not
think that you ever get 16 player packets in one update.
That leaves you with some more "weaponsdata" :-)
If you have another protocol you must compute the overhead by
yourself.
And any limit smaller than 500 bytes /update means that after
an UpdateAll the next update is skipped.
****************************************************************************
Variable and short packet justification: The three largest contributors
to netrek bandwidth are the packets SP_PLAYER (all player movement),
SP_YOU (information relating to your ship statistics, and your status)
and SP_TORP (torp movement). In one test I got these statistics:
SP_PLAYER: 2407 K
SP_YOU: 1408 K
SP_TORP: 1118 K
SP_STATS: 262 K
SP_FLAGS: 148 K
SP_WARNING: 139 K
SP_TORP_INFO: 90 K
SP_MESSAGE: 82 K,
... (the remaining packets account for about 50K)
Without much doubt, the first three (SP_PLAYER, SP_YOU, SP_TORP) contribute
most of the overhead. So...
NEW PACKETS:
ORIGINAL SIZE (bytes) NEW SIZE (bytes)
--------------------------------------------------------------
SP_PLAYER 12 SP_S_PLAYER 4 (**)
SP_YOU 32 SP_S_YOU 12
SP_S_YOU_SS 12
SP_TORP 12 SP_S_TORP ~4 (***)
SP_TORP_INFO 8 SP_S_TORPINFO 1
SP_PLANET 12 SP_S_PLANET 6 (*)
SP_MESSAGE 84 SP_S_MESSAGE 8-76
SP_WARNING 84 SP_S_WARNING 4
(*) variable packets, each packet containing 2 bytes of type & length
information and some number of 6-byte entries,
(**) variable packets, each packet containing 4 (or 12) bytes of type & length
information and some number of 4-byte entries,
(***) The torp packet is really a packet container for 9 bit pixelcoordinates.
Look into the code to figure out :-)
Notice that the reduction in network traffic is very close to 40-70% of
the original.
SP_S_PLAYER: byte bit description
-----------------------
0 0-4 player number, 5 local or galactic, 6 = 9. x-bit, 7 9. y-bit
1 0-3 speed, 4-7 direction of ship
2 0-7 low 8 bits from X-Pixelcoordinate
3 0-7 low 8 bits from Y-Pixelcoordinate
SP_S_TORP: byte range
-----------------------
0 0-7 Packettype
1 0-7 Bitset describing which torps are in this packet.
2 0-7 Torpnumber of first torp( num*8=torpnumber)
3 A number of 9 Bit pairs. Each describing one
torp.
( The 9 bit numbers are the torpcoordinates in
pixel-coordinates.)
All rounded up to 4 byte boundaries.
SP_S_YOU and SP_S_YOU_SS are the result of dividing SP_YOU into two
packets. Most of the time, SP_YOU gets sent because ship status has
changed, i.e. damage, fuel, or shields. The remaining information,
hostile, swar, armies, and flags are not needed as often. Therefore it
makes sense to split SP_YOU into two packets:
struct youshort_spacket { /* SP_S_YOU */
char type;
char pnum;
char hostile;
char swar;
char armies;
char whydead;
char whodead;
char pad1;
unsigned flags;
};
and
struct youss_spacket { /* SP_S_YOU_SS */
char type;
char pad1;
unsigned short damage;
unsigned short shield;
unsigned short fuel;
unsigned short etemp;
unsigned short wtemp;
};
The new SP_S_PLANET: All info as in the old packet but only 255 armies.
struct planet_s_spacket { /* body of SP_S_PLANET */
char pnum;
char owner;
char info;
uchar armies; /* more than 255 Armies ? ... */
short flags;
};
struct warning_s_spacket { /* SP_S_WARNING */
char type;
uchar whichmessage;
char argument, argument2; /* for phaser etc ... */
};
Instead of sending the strings i send only an index into an string array.
This works also for all weapons warnings with arguments. (like Phaser.)
(eg: old: Phaserpacket (16) + SP_WARNING = 100 bytes. now only 20.)
Limitations: Only 64 Players can be send with SP_S_PLAYER.
