260 lines
9.1 KiB
Nim
260 lines
9.1 KiB
Nim
## # Tron example
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##
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## In this tutorial, we will create a video game based on libp2p, using
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## all of the features we talked about in the last tutorials.
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##
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## We will:
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## - Discover peers using the Discovery Manager
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## - Use GossipSub to find a play mate
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## - Create a custom protocol to play with him
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##
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## While this may look like a daunting project, it's less than 150 lines of code.
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##
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## The game will be a simple Tron. We will use [nico](https://github.com/ftsf/nico)
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## as a game engine. (you need to run `nimble install nico` to have it available)
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##
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## 
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##
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## We will start by importing our dependencies and creating our types
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import os
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import nico, chronos, stew/byteutils, stew/endians2
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import libp2p
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import libp2p/protocols/rendezvous
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import libp2p/discovery/rendezvousinterface
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import libp2p/discovery/discoverymngr
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const
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directions = @[(K_UP, 0, -1), (K_LEFT, -1, 0), (K_DOWN, 0, 1), (K_RIGHT, 1, 0)]
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mapSize = 32
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tickPeriod = 0.2
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type
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Player = ref object
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x, y: int
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currentDir, nextDir: int
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lost: bool
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color: int
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Game = ref object
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gameMap: array[mapSize * mapSize, int]
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tickTime: float
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localPlayer, remotePlayer: Player
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peerFound: Future[Connection]
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hasCandidate: bool
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tickFinished: Future[int]
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GameProto = ref object of LPProtocol
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proc new(_: type[Game]): Game =
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# Default state of a game
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result = Game(
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tickTime: -3.0, # 3 seconds of "warm-up" time
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localPlayer: Player(x: 4, y: 16, currentDir: 3, nextDir: 3, color: 8),
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remotePlayer: Player(x: 27, y: 16, currentDir: 1, nextDir: 1, color: 12),
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peerFound: newFuture[Connection]()
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)
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for pos in 0 .. result.gameMap.high:
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if pos mod mapSize in [0, mapSize - 1] or pos div mapSize in [0, mapSize - 1]:
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result.gameMap[pos] = 7
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## ## Game Logic
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## The networking during the game will work like this:
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##
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## * Each player will have `tickPeriod` (0.1) seconds to choose
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## a direction that he wants to go to (default to current direction)
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## * After `tickPeriod`, we will send our choosen direction to the peer,
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## and wait for his direction
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## * Once we have both direction, we will "tick" the game, and restart the
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## loop, as long as both player are alive.
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##
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## This is a very simplistic scheme, but creating proper networking for
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## video games is an [art](https://developer.valvesoftware.com/wiki/Latency_Compensating_Methods_in_Client/Server_In-game_Protocol_Design_and_Optimization)
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##
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## The main drawback of this scheme is that the more ping you have with
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## the peer, the slower the game will run. Or invertedly, the less ping you
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## have, the faster it runs!
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proc update(g: Game, dt: float32) =
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# Will be called at each frame of the game.
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#
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# Because both Nico and Chronos have a main loop,
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# they must share the control of the main thread.
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# This is a hacky way to make this happen
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waitFor(sleepAsync(1.milliseconds))
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# Don't do anything if we are still waiting for an opponent
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if not(g.peerFound.finished()) or isNil(g.tickFinished): return
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g.tickTime += dt
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# Update the wanted direction, making sure we can't go backward
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for i in 0 .. directions.high:
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if i != (g.localPlayer.currentDir + 2 mod 4) and keyp(directions[i][0]):
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g.localPlayer.nextDir = i
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if g.tickTime > tickPeriod and not g.tickFinished.finished():
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# We choosen our next direction, let the networking know
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g.localPlayer.currentDir = g.localPlayer.nextDir
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g.tickFinished.complete(g.localPlayer.currentDir)
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proc tick(g: Game, p: Player) =
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# Move player and check if he lost
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p.x += directions[p.currentDir][1]
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p.y += directions[p.currentDir][2]
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if g.gameMap[p.y * mapSize + p.x] != 0: p.lost = true
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g.gameMap[p.y * mapSize + p.x] = p.color
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proc mainLoop(g: Game, peer: Connection) {.async.} =
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while not (g.localPlayer.lost or g.remotePlayer.lost):
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if g.tickTime > 0.0:
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g.tickTime = 0
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g.tickFinished = newFuture[int]()
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# Wait for a choosen direction
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let dir = await g.tickFinished
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# Send it
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await peer.writeLp(toBytes(uint32(dir)))
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# Get the one from the peer
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g.remotePlayer.currentDir = int uint32.fromBytes(await peer.readLp(8))
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# Tick the players & restart
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g.tick(g.remotePlayer)
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g.tick(g.localPlayer)
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## We'll draw the map & put some texts when necessary:
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proc draw(g: Game) =
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for pos, color in g.gameMap:
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setColor(color)
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boxFill(pos mod 32 * 4, pos div 32 * 4, 4, 4)
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let text = if not(g.peerFound.finished()): "Matchmaking.."
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elif g.tickTime < -1.5: "Welcome to Etron"
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elif g.tickTime < 0.0: "- " & $(int(abs(g.tickTime) / 0.5) + 1) & " -"
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elif g.remotePlayer.lost and g.localPlayer.lost: "DEUCE"
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elif g.localPlayer.lost: "YOU LOOSE"
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elif g.remotePlayer.lost: "YOU WON"
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else: ""
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printc(text, screenWidth div 2, screenHeight div 2)
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## ## Matchmaking
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## To find an opponent, we will broadcast our address on a
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## GossipSub topic, and wait for someone to connect to us.
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## We will also listen to that topic, and connect to anyone
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## broadcasting his address.
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##
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## If we are looking for a game, we'll send `ok` to let the
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## peer know that we are available, check that he is also available,
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## and launch the game.
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proc new(T: typedesc[GameProto], g: Game): T =
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proc handle(conn: Connection, proto: string) {.async, gcsafe.} =
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defer: await conn.closeWithEof()
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if g.peerFound.finished or g.hasCandidate:
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await conn.close()
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return
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g.hasCandidate = true
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await conn.writeLp("ok")
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if "ok" != string.fromBytes(await conn.readLp(1024)):
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g.hasCandidate = false
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return
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g.peerFound.complete(conn)
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# The handler of a protocol must wait for the stream to
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# be finished before returning
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await conn.join()
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return T(codecs: @["/tron/1.0.0"], handler: handle)
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proc networking(g: Game) {.async.} =
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# Create our switch, similar to the GossipSub example and
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# the Discovery examples combined
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let
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rdv = RendezVous.new()
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switch = SwitchBuilder.new()
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.withRng(newRng())
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.withAddresses(@[ MultiAddress.init("/ip4/0.0.0.0/tcp/0").tryGet() ])
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.withTcpTransport()
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.withYamux()
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.withNoise()
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.withRendezVous(rdv)
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.build()
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dm = DiscoveryManager()
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gameProto = GameProto.new(g)
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gossip = GossipSub.init(
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switch = switch,
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triggerSelf = false)
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dm.add(RendezVousInterface.new(rdv))
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switch.mount(gossip)
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switch.mount(gameProto)
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gossip.subscribe(
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"/tron/matchmaking",
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proc (topic: string, data: seq[byte]) {.async.} =
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# If we are still looking for an opponent,
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# try to match anyone broadcasting it's address
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if g.peerFound.finished or g.hasCandidate: return
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g.hasCandidate = true
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try:
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let
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(peerId, multiAddress) = parseFullAddress(data).tryGet()
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stream = await switch.dial(peerId, @[multiAddress], gameProto.codec)
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await stream.writeLp("ok")
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if (await stream.readLp(10)) != "ok".toBytes:
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g.hasCandidate = false
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return
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g.peerFound.complete(stream)
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# We are "player 2"
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swap(g.localPlayer, g.remotePlayer)
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except CatchableError as exc:
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discard
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)
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await switch.start()
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defer: await switch.stop()
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# As explained in the last tutorial, we need a bootnode to be able
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# to find peers. We could use any libp2p running rendezvous (or any
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# node running tron). We will take it's MultiAddress from the command
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# line parameters
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if paramCount() > 0:
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let (peerId, multiAddress) = paramStr(1).parseFullAddress().tryGet()
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await switch.connect(peerId, @[multiAddress])
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else:
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echo "No bootnode provided, listening on: ", switch.peerInfo.fullAddrs.tryGet()
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# Discover peers from the bootnode, and connect to them
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dm.advertise(RdvNamespace("tron"))
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let discoveryQuery = dm.request(RdvNamespace("tron"))
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discoveryQuery.forEach:
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try:
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await switch.connect(peer[PeerId], peer.getAll(MultiAddress))
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except CatchableError as exc:
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echo "Failed to dial a peer: ", exc.msg
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# We will try to publish our address multiple times, in case
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# it takes time to establish connections with other GossipSub peers
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var published = false
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while not published:
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await sleepAsync(500.milliseconds)
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for fullAddr in switch.peerInfo.fullAddrs.tryGet():
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if (await gossip.publish("/tron/matchmaking", fullAddr.bytes)) == 0:
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published = false
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break
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published = true
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discoveryQuery.stop()
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# We now wait for someone to connect to us (or for us to connect to someone)
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let peerConn = await g.peerFound
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defer: await peerConn.closeWithEof()
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await g.mainLoop(peerConn)
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let
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game = Game.new()
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netFut = networking(game)
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nico.init("Status", "Tron")
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nico.createWindow("Tron", mapSize * 4, mapSize * 4, 4, false)
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nico.run(proc = discard, proc(dt: float32) = game.update(dt), proc = game.draw())
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waitFor(netFut.cancelAndWait())
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## And that's it! If you want to run this code locally, the simplest way is to use the
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## first node as a boot node for the second one. But you can also use any rendezvous node
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