How client-server architecture works on Roblox — Transcript

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1. 0:00This video is for developers who have
2. 0:01experience with other game engines, but
3. 0:03are new to Roblox. If you've used other
4. 0:06engines, adapting to Roblox's
5. 0:07client-server architecture can require
6. 0:09[music] a bit of a shift in mindset.
7. 0:11Let's discuss why.
8. 0:13Hey everyone, it's Andrew from Roblox.
9. 0:15What I have here is a demo experience
10. 0:17generously provided by Mr. Chicken
11. 0:19Rocket and Dev Odysseus. It's a
12. 0:21twin-stick shooter, a genre that I
13. 0:22imagine many of you are familiar with.
14. 0:24You shoot skeletons with friends, revel
15. 0:26in the chaos, and grab gems. Let's dig
16. 0:29into some key features of this
17. 0:30experience, and along the way we can
18. 0:32talk more broadly about developing on
19. 0:33Roblox. It's a lot. I want to cover a
20. 0:36lot. We'll talk about the following.
21. 0:42Let's start [music] with project
22. 0:43architecture. The first, maybe most
23. 0:45important point to understand when
24. 0:47getting started with Roblox is that the
25. 0:48client-server architecture means that
26. 0:50the server owns everything. As you build
27. 0:54in Studio, what you're looking at is the
28. 0:56server's view of the world. [music] The
29. 0:57client then gets some subset of that
30. 1:00view depending on the situation, and can
31. 1:02make its own local-only changes for
32. 1:03things like the user interface and
33. 1:05visual effects. [music]
34. 1:07This architecture means there are a
35. 1:09whole bunch of places to put scripts. We
36. 1:11have not one, but two other videos on
37. 1:13this subject. Check them out if you want
38. 1:15to get into the nitty-gritty. The basics
39. 1:17are that server scripts go in server
40. 1:19script service, and client scripts go
41. 1:21[music] in replicated storage with a run
42. 1:23context of client. Shared module scripts
43. 1:26also go in replicated storage.
44. 1:28As we switch between the client and the
45. 1:30server in Studio, you can see right away
46. 1:32that the contents of server script
47. 1:34service and server storage just aren't
48. 1:36on the client. The difference is even
49. 1:38more stark if you test an experience
50. 1:40that uses streaming and enable the free
51. 1:42cam with shift P. In addition to not
52. 1:44having everything you saw on the server
53. 1:46while editing the experience, [music]
54. 1:48you can see here that the client only
55. 1:49has a subset of the whole workspace.
56. 1:51When we start building, the first step
57. 1:53is to give ourselves some objects to
58. 1:55[music] work with. Mr. Chicken Rocket
59. 1:57calls this mental scaffolding, a term I
60. 1:59love, but the more prosaic way to think
61. 2:01about it is that games are all about
62. 2:03interactivity,
63. 2:04>> [music]
64. 2:04>> and it's hard to add interactivity to
65. 2:06objects that don't exist. If you want to
66. 2:08build a twin-stick shooter with a
67. 2:10procedural layout and destructible
68. 2:11objects, the first step is to build some
69. 2:14rooms.
70. 2:15Before we start scripting, let's get
71. 2:17comfortable. You can absolutely use the
72. 2:19built-in script editor, but if you're an
73. 2:21experienced developer, you probably have
74. 2:23a preferred [music] text editor. Taking
75. 2:25the time to set up script sync means
76. 2:27that you can use your favorite editor
77. 2:28and your favorite coding tools. Here
78. 2:31I've synced everything to my local disk
79. 2:32[music] and open the project in Cursor.
80. 2:35Because it's on my local disk, I can use
81. 2:36Git or any other version control system.
82. 2:39Depending on how deep you are down the
83. 2:41AI rabbit hole, and and listen, I'm not
84. 2:43judging either way, you might also want
85. 2:45to hook up the Studio MCP server to
86. 2:47Claude.
87. 2:48You might be tempted to start putting
88. 2:49scripts directly onto objects in the
89. 2:51workspace, but it inevitably leads to a
90. 2:53maintenance nightmare as you start
91. 2:55duplicating models. Instead, tag the
92. 2:57parts you need to reason around and use
93. 2:59the collection service to gather them up
94. 3:01so you can work with them in a single
95. 3:03place. Rather than running every frame,
96. 3:05code in Roblox tends to be more
97. 3:07event-driven, so you listen for changes
98. 3:09>> [music]
99. 3:10>> and then run some code.
100. 3:11Speaking of events, communication
101. 3:13between the client and the server occurs
102. 3:16using what are called remote events. We
103. 3:17have a video on this subject, too. Link
104. 3:19in the description.
105. 3:21Here, the client performs all sorts of
106. 3:23work to create a compelling visual for
107. 3:24the player. It [music] takes a broken
108. 3:26child model within the original model
109. 3:28and adds it to a debris table.
110. 3:30When a bullet hits the model, the script
111. 3:32swaps it for the broken one, [music]
112. 3:34unanchors the parts so that physics
113. 3:35apply, and then makes them go flying.
114. 3:37Give those parts a randomized ejection
115. 3:39vector.
116. 3:41A simple particle effect then amps up
117. 3:43the sense of destruction.
118. 3:44Finally, though, the client script
119. 3:46notifies the server, "Hey, player one
120. 3:48broke this object." using a remote
121. 3:50event. In response, the server
122. 3:52replicates the action to all other
123. 3:53clients, spawns loot only for player
124. 3:56one, and then destroys the object. The
125. 3:58final situation is very instructive. On
126. 4:01player one, we see debris and a few
127. 4:03gems. On player two, just the debris,
128. 4:05but critically, it's [music] different
129. 4:06debris due to the random nature of the
130. 4:08client code. On the server, we don't see
131. 4:10anything at all because the server is
132. 4:12keeping track of state, not visuals.
133. 4:15There's also general housekeeping, most
134. 4:17of which uses the player and character
135. 4:19events. When a player joins for the
136. 4:21first time, initialize their data. If
137. 4:23they're returning, load their data from
138. 4:25a data store. Manipulate that data over
139. 4:27the course of their session and save it
140. 4:28when they leave. Do you plan to
141. 4:30implement your own character solution or
142. 4:32use default avatars?
143. 4:34Will players use the built-in spawn
144. 4:36system, [music] or do you need to create
145. 4:37your own? It's not the most exciting
146. 4:40scripting work in the world, but it
147. 4:41creates the
148. 4:42testable skeleton of of your experience.
149. 4:45Or whatever metaphor you prefer.
150. 4:47There are a couple other key features to
151. 4:49mention, but they're situational. First,
152. 4:51[music] streaming. If players can see
153. 4:53beyond 100 m or so, that's 357 studs in
154. 4:57Roblox parlance, you probably want to
155. 4:59enable streaming. I mention streaming
156. 5:01all the time on this channel and
157. 5:02probably need to have my title changed
158. 5:04>> [music]
159. 5:04>> to chief streaming evangelist, but a big
160. 5:06gotcha with streaming is to organize
161. 5:08your instances into models and mark them
162. 5:10as atomic. Marking models as atomic
163. 5:13means that clients get the whole model
164. 5:14or none of it, which makes it
165. 5:16dramatically easier to reason around the
166. 5:18modeling code. Imagine a house streaming
167. 5:20in incrementally so you get the walls
168. 5:22and the floor, and then a few
169. 5:24milliseconds later the roof and the
170. 5:25doors, and then the windows follow a
171. 5:27quarter second after that. It'd be a
172. 5:29nightmare to code around. You want your
173. 5:31scripts to be only minimally aware of
174. 5:33the part composition of a model rather
175. 5:35than having to constantly check to make
176. 5:37sure they have everything they need.
177. 5:39The other key feature is server
178. 5:41authority. If you're designing a
179. 5:42competitive multiplayer experience,
180. 5:44check out server authority. It prevents
181. 5:46entire classes of cheats like fly hacks
182. 5:49and speed hacks [music]
183. 5:50by not trusting clients to report their
184. 5:52position or state. It moves ownership of
185. 5:55the player from the client, where they
186. 5:56can cheat, to the server, where they
187. 5:58can't.
188. 5:59It's too much to cover here and still in
189. 6:01beta, but I'll link to the documentation
190. 6:03in the description, which has three
191. 6:05sample games to help you understand the
192. 6:06difference in project structure when
193. 6:08server authority is enabled.
194. 6:11To close things out, let's review two
195. 6:12more features from this experience.
196. 6:14[music]
197. 6:14Procedural generation and
198. 6:17gates.
199. 6:18As you can see here, our view in
200. 6:20building in Studio is quite different
201. 6:22from the in-game view.
202. 6:24You don't have to do this, of course,
203. 6:25but if you want a procedural world, you
204. 6:27can create any number of discrete
205. 6:28building blocks, and then have the
206. 6:30server put them together at runtime.
207. 6:32Rather than [music] each client having
208. 6:34to do that work locally, they all just
209. 6:35get the version the server created.
210. 6:37Here, we have a server script that
211. 6:39initializes the experience. It passes a
212. 6:41desired room count and a random seed to
213. 6:44the map gen module. Everything is
214. 6:46hardcoded here for demo purposes, but
215. 6:48could just as easily be random. [music]
216. 6:50The module script starts by taking every
217. 6:52room and hallway in the prefabs folder
218. 6:54and sticking them into tables so they're
219. 6:56easy to work with.
220. 6:57After some cleanup, you can see that it
221. 6:59adds hallways and rooms until it reaches
222. 7:01the desired number. If it runs out of
223. 7:03unique rooms, it starts duplicating.
224. 7:05Add hallway and room mostly deals with
225. 7:07orientation and clearing rooms that have
226. 7:10already been used from the table to make
227. 7:12sure you don't get the same room over
228. 7:13and over due to bad luck with
229. 7:14randomization. And voila, a layout. And
230. 7:17another, and another.
231. 7:19Gates sure seem like they should be
232. 7:21easy, but the implementation here shows
233. 7:23off the separation of server and client
234. 7:25concerns really well. You can see that
235. 7:27we have a grill positioned below the
236. 7:29map, and when we enter a room, the
237. 7:30server sets the closed attribute on that
238. 7:32grill to true or false. Then the client
239. 7:35takes over.
240. 7:36In what you might describe as a
241. 7:38suboptimal approach, the client checks
242. 7:40every grill once per frame to see if
243. 7:42it's current open or closed state
244. 7:44differs from the closed attribute that
245. 7:45the server set. If the state differs,
246. 7:48get the open and closed positions from
247. 7:50the grill spot open and grill spot
248. 7:52closed attachments, and play that tween.
249. 7:55Is there a way to make this process
250. 7:56event-driven rather than checking every
251. 7:58frame? Probably yes, but but that's game
252. 8:01development. Even if we look at it and
253. 8:03think we can do better, optimizing
254. 8:04[music]
255. 8:05this module might not yield any tangible
256. 8:07performance gains. We're only going to
257. 8:09have a few gates at a time, so it's
258. 8:10probably [music] better to just keep the
259. 8:12simpler code. We can't let the perfect
260. 8:14be the enemy of the good, or the good be
261. 8:16the enemy of the
262. 8:17You know what? I'm actually going to go
263. 8:19back and see if I can rewrite that
264. 8:20module.
265. 8:22For so much more on how to work within
266. 8:23Roblox's client-server architecture,
267. 8:25check out the documentation at
268. 8:27create.roblox.com.
269. 8:29I want to extend a huge thank you to Mr.
270. 8:31Chicken Rocket and Dev Odysseus for all
271. 8:34their help and support on this video,
272. 8:36and an equally large thanks to all of
273. 8:37you for watching.
274. 8:38See you next time.