1. CSE 5912 Networking Tech Talk Mike Alquist.2 Glen Gainer.25 Austin Neidert.13

2. Before Internet □ Time-Sharing □ Host-based □ LAN / Ethernet □ Peer-to-peer

3. Time-Sharing □PLATO □ Empire ■ Wargame similar to Risk ■ Text based

4. Host-Based □ MUD ■ Roy Trubshaw ■ Text-based RPG Adventure ■ Multiple users on one network

5. Peer-to-Peer Networks □ Maze War □ https://youtu.be /7chDIySXK2Q?t =2m20s https://youtu.be /7chDIySXK2Q?t =2m20s □ 2:20

6. LAN / Ethernet □ SGI Dogfight ■ Developed 1983 ■ 1984 - Local Network capabilities ■ 1986 - UDP broadcast capability added ■ 1989 - IP Multicast capability (224.0.1.2)

7. Eventually, Internet □ College → Industry □ Burst of Multiplayer Games □ Disks → Online Software □ Facebook Games

8. Notable Games □ Neverwinter Nights □ Doom □ Quake □ Command & Conquer □ Diablo □ Counter Strike

9. Use Case: Counter Strike Updates □ Problem: Updates, version mismatches, cheating, licensing □ Solution: Steam ■ Buy games online ■ Scheduled updates ■ VAC □ Downloads immediate data ■ Ability to rollback □ Requires broadband connection

10. With the Internet Came Risks □ Piracy □ Network Security Issues ■ Technological Risks (Malware) ■ Social Risks (Social Engineering) □ Data Breaches ■ PlayStation Network (2011) ■ Steam (2015)

11. Data Breach Use Case: PlayStation Network □ External Intrusion (Anonymous?) □ 77 Million Users Affected □ Network down for 23 days □ Sony releases patch 3.61 to fix security issues ■ Still didn’t go online □ May 14th - Service restoration

12. Internet Layers Application Transport Network Link Physical 5 Layer Model

13. Physical Layer  How to send bits out over a cable Twisted Pair CableFiber Optic Cable

14. Link Layer  How to make sure bits get across safely between two machines Ethernet frame Preamble for Synchronization & Flow control CRC for Error checking Data defined in higher network layer

15. Network Layer  How to make sure bits get to the right machine in whole network

16. Transportation Layer  TCP – Transmission Control Protocol  UDP – User Datagram Protocol

17. UDP - User Datagram Protocol  a.k.a Unreliable Datagram Protocol  Connectionless / Datagram Based

18. TCP - Transmission Control Protocol  Reliable  Connection Oriented / Stream Based

19. TCP Details (3 Way Handshake)

20. TCP Details (Sending Data) Alternating BitSliding Window Request / Data ACK

21. TCP Details (Closing Connection)

22. Which protocol UDP/TCP to use?

23. Application Layer  How to interpret the bits

24. Questions so far?  Send us an ACKnowledgement of understanding before we present the next packet of information to you.  Or help us stall for time, your choice.

25. Implementation in Games □ Basic communication □ Basic game models □ Problems that arise as a result of networking □ Socket Libraries

26. Basic Communication □Players send messages □Players receive messages ■ need to be handled □Command Pattern used often

27. Basic Game Models □ MMO ■ Server/Client □ Matchmade Game/First Person Shooter ■ Server/Client ■ Some clients act as a server for their game

28. Problems □ Socket Exceptions □ Threading Problems □ Point Interpolation □ Back to Back Messages □ Port Forwarding □ Cheating

29. Socket Exceptions □ socket.accept() ■ server initialization ■ incorrect protocol ■ socket already bound

30. Socket Exceptions □ socket.connect() ■ server can’t be reached ■ incorrect IP address ■ incorrect port ■ not port forwarded ■ server never started

31. Socket Exceptions □ socket.send() ■ unexpected disconnection

32. Socket Exceptions □ socket.receive() ■ unexpected disconnection ■ end of stream □ null message □ empty message □ -1 returned

33. Threading Problems □Blocking I/O □Accessing resources with separate threads ■ message buffer ■ semaphores ■ check for null □Game logic in Unity needs to be handled in the main thread

34. Point Interpolation □Smooth look and feel □Continuous variables ■ location □State related problems ■ animation

35. Back to Back Messages □socket.send() gets called faster than socket.receive() can be called and handled

36. Port Forwarding □ When hosting a server □ Static internal IP address □ Static external IP address □ No-IP

37. Cheating □ Let server handle important game play □ Server verifies clients’ actions are valid before telling other clients □ Client uses necessary information for display

38. Socket Libraries -.Net Sockets □ Lower level □ Sends and receives byte arrays □ All message handling is left to the programmer □ All serialization is left to the programmer

39. Socket Libraries - UNet □Higher level □Done for you ■ some sending ■ some receiving ■ some handling ■ some serialization □Also has classes that allow the programmer to do manual sending and handling

40. Socket Libraries - UNet

41. □ Important classes ■ NetworkBehaviour □ [Server] □ [Client] □ [SyncVar] ■ NetworkTransform ■ NetworkProximityChecker □ Authority properties

42. Socket Libraries - UNet □ Attribute Examples

43. Final Questions?