Presentation about our studies on some game network concepts and optimizations used by some games.

1. Game network
programming
PotHix (Willian Molinari)
Diego Souza (marciano)

2. Why?

4. Skeleton Jigsaw: http://plaev.me/skeleton-jigsaw
Shameless self promotion

5. To have fun, bro!

6. Agenda
■ Synchronous RTS
■ Peer to peer
■ Client / server
■ UDP
■ Quake strategy
■ TCP
■ Web and HTML5

7. Synchronous RTS

8. RTS's and Supreme commander

9. Peer to peer

10. Everything in sync

11. Two gameloops!

12. Latency
My life for the horde!

13. Player1 Player2 Player3
tick 0ms
tick 100ms
tick 200ms
tick 300ms
tick 400ms

14. Player1 Player2 Player3
tick 0ms
tick 100ms
tick 200ms
tick 300ms
tick 400ms

15. Player1 Player2 Player3
tick 0ms
tick 100ms
tick 200ms
tick 300ms
tick 400ms

16. Player1 Player2 Player3
tick 0ms
tick 100ms
tick 200ms
tick 300ms
tick 400ms

17. butterfly effect

18. So...

19. Player1 Player2 Player3
tick 0ms
tick 100ms
tick 200ms
tick 300ms
tick 400ms

20. Player1 Player2 Player3
tick 0ms
tick 100ms
UI OK!
tick 200ms
tick 300ms
tick 400ms

21. Desync

22. Age of empires
1500 archers with a 28.8 modem [1]

23. Client / Server

24. Authoritative server

25. Client Server
pos (0,0)

26. Client Server
pos (0,0)
pos (0,0)

27. Client Server
pos (0,0)
pos (0,0)
move
pos (1,0)

28. Client Server
pos (0,0)
pos (0,0)
move
pos (1,0)
pos (1,0)

29. Smartass

30. Client Server
pos (0,0)

31. Client Server
pos (0,0)
pos (0,0)

32. Client Server
pos (0,0)
pos (0,0)
move
pos (100,200)

33. Client Server
pos (0,0)
pos (0,0)
move
pos (100,200)
pos (100,200)

35. Client Server
pos (0,0)

36. Client Server
pos (0,0)
pos (0,0)

37. Client Server
pos (0,0)
pos (0,0)
move right
pos (1,0)

38. Client Server
pos (0,0)
pos (0,0)
move right
pos (1,0)
pos (1,0)

39. Victory!

40. Client side prediction

41. Client Server
pos (0,0)

42. Client Server
pos (0,0)
pos (0,0)

43. Client Server
pos (0,0)
pos (0,0)
move right
pos (1,0)

44. Client Server
pos (0,0)
pos (0,0)
move right
pos (1,0)
pos (1,0)

45. Client Server
pos (0,0)
pos (0,0)
move right
Latency pos (1,0)
pos (1,0)

46. Client Server
pos (0,0)
pos (0,0)
move right
Animation pos (1,0)
pos (1,0)
Predicting

47. Client Server
pos (0,0)
pos (0,0)
move right
Animation pos (1,0)
pos (1,0)
Predicting

48. Client Server
pos (0,0)
pos (0,0)
move right
Animation pos (2,0)
pos (1,0)

49. Client Server
pos (0,0)
pos (0,0)
move right
Animation pos (2,0)
pos (1,0)
Correction
pos (2,0)

50. Quake
https://github.com/id-Software

51. UDP
datagrams, unreliable, unordered

52. rcv_buf >= snd_buf
All receive operations return only one packet
watch out for MSG_TRUNC

53. auto ip_mtu_discover
enabled by default
EMSGSIZE signals packet too big

54. 65k max theoretical packet
limit (headers included)
rfc defines the size header to 16bits

55. however, 1472 is likely the
max you may get, 576 to be
sure
MTU - headers

56. remember the TOS
throughput, reliability, lowdelay (etc.)

57. Quake world
https://github.com/id-Software/Quake

58. All credits to Fabien Sanglard: http://fabiensanglard.net/quakeSource/quakeSourceNetWork.php
Code: https://github.com/id-Software/Quake/blob/master/QW/client/net_chan.c

59. Quake III arena
https://github.com/id-Software/Quake-III-Arena

60. Snapshots based

61. All credits to Fabien Sanglard: http://fabiensanglard.net/quake3/network.php

62. All credits to Fabien Sanglard: http://fabiensanglard.net/quake3/network.php

63. All credits to Fabien Sanglard: http://fabiensanglard.net/quake3/network.php

64. All credits to Fabien Sanglard: http://fabiensanglard.net/quake3/network.php

65. All credits to Fabien Sanglard: http://fabiensanglard.net/quake3/network.php

66. All credits to Fabien Sanglard: http://fabiensanglard.net/quake3/network.php

67. Open source code!
https://github.com/id-Software/Quake-III-Arena/blob/master/code/qcommon/msg.c

68. TCP
Streaming, reliable, connection oriented

69. TCP tuning

70. Long story short: use auto-tune
You probably just need to tune the maximum values
(system wide)

71. High-performance extensions
refer to rfc1323

72. Bandwidth-delay product
data link's capacity (in bits per second) and its end-to-
end delay (in seconds).

73. 10Mbs x 1ms = 1.22 KB
10Mbs x 200ms = 244 KB
rfc1323: huge buffers

74. CORK
don't send partial frames

75. NODELAY
disable nagle's algorithm

76. socket options

77. https://gist.github.com/4036204

78. benchmarking

81. BBG* and HTML5
*Browser based games

82. The same thing...
...but not...

83. No TCP
No UDP
No peer to peer

84. Chrome support!?
http://developer.chrome.com/apps/app_network.html

85. HTTP

86. Websockets

87. Mozilla multiplayer game: http://browserquest.mozilla.org

88. Blackberry
browser
Chrome
Opera
Mobile safari
Browsers
IE
Android browser
Firefox
Opera mini
Safari

89. Caniuse.com: websockets marketshare

90. Socket.io
Fallbacks all over the place

91. Bandwidth
We're back again

92. References
■ [1] Age of empires paper
■ Synchronous RTS engines
■ Client / server tricks
■ Quake code reviews
■ Improving bandwidth for websockets
■ Unreal networking architecture
■ http://tools.ietf.org/html/rfc1323

93. References
■ http://linux.die.net/man/7/udp
■ http://linux.die.net/man/7/ip
■ http://linux.die.net/man/7/socket
■ http://en.wikipedia.org/wiki/Nagle's_algorithm
■ http://en.wikipedia.org/wiki/Bandwidth-
delay_product

94. References
■ http://tools.ietf.org/html/rfc1046
■ http://linux.die.net/man/7/tcp

95. Game over