nim-libp2p/examples/tutorial_6_game.nim

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## # Tron example
##
## In this tutorial, we will create a video game based on libp2p, using
## all of the features we talked about in the last tutorials.
##
## We will:
## - Discover peers using the Discovery Manager
## - Use GossipSub to find a play mate
## - Create a custom protocol to play with him
##
## While this may look like a daunting project, it's less than 150 lines of code.
##
## The game will be a simple Tron. We will use [nico](https://github.com/ftsf/nico)
## as a game engine. (you need to run `nimble install nico` to have it available)
##
## ![multiplay](https://user-images.githubusercontent.com/13471753/198852714-b55048e3-f233-4723-900d-2193ad259fe1.gif)
##
## We will start by importing our dependencies and creating our types
import os
import nico, chronos, stew/byteutils, stew/endians2
import libp2p
import libp2p/protocols/rendezvous
import libp2p/discovery/rendezvousinterface
import libp2p/discovery/discoverymngr
const
directions = @[(K_UP, 0, -1), (K_LEFT, -1, 0), (K_DOWN, 0, 1), (K_RIGHT, 1, 0)]
mapSize = 32
tickPeriod = 0.2
type
Player = ref object
x, y: int
currentDir, nextDir: int
lost: bool
color: int
Game = ref object
gameMap: array[mapSize * mapSize, int]
tickTime: float
localPlayer, remotePlayer: Player
peerFound: Future[Connection]
hasCandidate: bool
tickFinished: Future[int]
GameProto = ref object of LPProtocol
proc new(_: type[Game]): Game =
# Default state of a game
result = Game(
tickTime: -3.0, # 3 seconds of "warm-up" time
localPlayer: Player(x: 4, y: 16, currentDir: 3, nextDir: 3, color: 8),
remotePlayer: Player(x: 27, y: 16, currentDir: 1, nextDir: 1, color: 12),
peerFound: newFuture[Connection]()
)
for pos in 0 .. result.gameMap.high:
if pos mod mapSize in [0, mapSize - 1] or pos div mapSize in [0, mapSize - 1]:
result.gameMap[pos] = 7
## ## Game Logic
## The networking during the game will work like this:
##
## * Each player will have `tickPeriod` (0.1) seconds to choose
## a direction that he wants to go to (default to current direction)
## * After `tickPeriod`, we will send our choosen direction to the peer,
## and wait for his direction
## * Once we have both direction, we will "tick" the game, and restart the
## loop, as long as both player are alive.
##
## This is a very simplistic scheme, but creating proper networking for
## video games is an [art](https://developer.valvesoftware.com/wiki/Latency_Compensating_Methods_in_Client/Server_In-game_Protocol_Design_and_Optimization)
##
## The main drawback of this scheme is that the more ping you have with
## the peer, the slower the game will run. Or invertedly, the less ping you
## have, the faster it runs!
proc update(g: Game, dt: float32) =
# Will be called at each frame of the game.
#
# Because both Nico and Chronos have a main loop,
# they must share the control of the main thread.
# This is a hacky way to make this happen
waitFor(sleepAsync(1.milliseconds))
# Don't do anything if we are still waiting for an opponent
if not(g.peerFound.finished()) or isNil(g.tickFinished): return
g.tickTime += dt
# Update the wanted direction, making sure we can't go backward
for i in 0 .. directions.high:
if i != (g.localPlayer.currentDir + 2 mod 4) and keyp(directions[i][0]):
g.localPlayer.nextDir = i
if g.tickTime > tickPeriod and not g.tickFinished.finished():
# We choosen our next direction, let the networking know
g.localPlayer.currentDir = g.localPlayer.nextDir
g.tickFinished.complete(g.localPlayer.currentDir)
proc tick(g: Game, p: Player) =
# Move player and check if he lost
p.x += directions[p.currentDir][1]
p.y += directions[p.currentDir][2]
if g.gameMap[p.y * mapSize + p.x] != 0: p.lost = true
g.gameMap[p.y * mapSize + p.x] = p.color
proc mainLoop(g: Game, peer: Connection) {.async.} =
while not (g.localPlayer.lost or g.remotePlayer.lost):
if g.tickTime > 0.0:
g.tickTime = 0
g.tickFinished = newFuture[int]()
# Wait for a choosen direction
let dir = await g.tickFinished
# Send it
await peer.writeLp(toBytes(uint32(dir)))
# Get the one from the peer
g.remotePlayer.currentDir = int uint32.fromBytes(await peer.readLp(8))
# Tick the players & restart
g.tick(g.remotePlayer)
g.tick(g.localPlayer)
## We'll draw the map & put some texts when necessary:
proc draw(g: Game) =
for pos, color in g.gameMap:
setColor(color)
boxFill(pos mod 32 * 4, pos div 32 * 4, 4, 4)
let text = if not(g.peerFound.finished()): "Matchmaking.."
elif g.tickTime < -1.5: "Welcome to Etron"
elif g.tickTime < 0.0: "- " & $(int(abs(g.tickTime) / 0.5) + 1) & " -"
elif g.remotePlayer.lost and g.localPlayer.lost: "DEUCE"
elif g.localPlayer.lost: "YOU LOOSE"
elif g.remotePlayer.lost: "YOU WON"
else: ""
printc(text, screenWidth div 2, screenHeight div 2)
## ## Matchmaking
## To find an opponent, we will broadcast our address on a
## GossipSub topic, and wait for someone to connect to us.
## We will also listen to that topic, and connect to anyone
## broadcasting his address.
##
## If we are looking for a game, we'll send `ok` to let the
## peer know that we are available, check that he is also available,
## and launch the game.
proc new(T: typedesc[GameProto], g: Game): T =
proc handle(conn: Connection, proto: string) {.async, gcsafe.} =
defer: await conn.closeWithEof()
if g.peerFound.finished or g.hasCandidate:
await conn.close()
return
g.hasCandidate = true
await conn.writeLp("ok")
if "ok" != string.fromBytes(await conn.readLp(1024)):
g.hasCandidate = false
return
g.peerFound.complete(conn)
# The handler of a protocol must wait for the stream to
# be finished before returning
await conn.join()
return T.new(codecs = @["/tron/1.0.0"], handler = handle)
proc networking(g: Game) {.async.} =
# Create our switch, similar to the GossipSub example and
# the Discovery examples combined
let
rdv = RendezVous.new()
switch = SwitchBuilder.new()
.withRng(newRng())
.withAddresses(@[ MultiAddress.init("/ip4/0.0.0.0/tcp/0").tryGet() ])
.withTcpTransport()
.withYamux()
.withNoise()
.withRendezVous(rdv)
.build()
dm = DiscoveryManager()
gameProto = GameProto.new(g)
gossip = GossipSub.init(
switch = switch,
triggerSelf = false)
dm.add(RendezVousInterface.new(rdv))
switch.mount(gossip)
switch.mount(gameProto)
gossip.subscribe(
"/tron/matchmaking",
proc (topic: string, data: seq[byte]) {.async.} =
# If we are still looking for an opponent,
# try to match anyone broadcasting it's address
if g.peerFound.finished or g.hasCandidate: return
g.hasCandidate = true
try:
let
(peerId, multiAddress) = parseFullAddress(data).tryGet()
stream = await switch.dial(peerId, @[multiAddress], gameProto.codec)
await stream.writeLp("ok")
if (await stream.readLp(10)) != "ok".toBytes:
g.hasCandidate = false
return
g.peerFound.complete(stream)
# We are "player 2"
swap(g.localPlayer, g.remotePlayer)
except CatchableError as exc:
discard
)
await switch.start()
defer: await switch.stop()
# As explained in the last tutorial, we need a bootnode to be able
# to find peers. We could use any libp2p running rendezvous (or any
# node running tron). We will take it's MultiAddress from the command
# line parameters
if paramCount() > 0:
let (peerId, multiAddress) = paramStr(1).parseFullAddress().tryGet()
await switch.connect(peerId, @[multiAddress])
else:
echo "No bootnode provided, listening on: ", switch.peerInfo.fullAddrs.tryGet()
# Discover peers from the bootnode, and connect to them
dm.advertise(RdvNamespace("tron"))
let discoveryQuery = dm.request(RdvNamespace("tron"))
discoveryQuery.forEach:
try:
await switch.connect(peer[PeerId], peer.getAll(MultiAddress))
except CatchableError as exc:
echo "Failed to dial a peer: ", exc.msg
# We will try to publish our address multiple times, in case
# it takes time to establish connections with other GossipSub peers
var published = false
while not published:
await sleepAsync(500.milliseconds)
for fullAddr in switch.peerInfo.fullAddrs.tryGet():
if (await gossip.publish("/tron/matchmaking", fullAddr.bytes)) == 0:
published = false
break
published = true
discoveryQuery.stop()
# We now wait for someone to connect to us (or for us to connect to someone)
let peerConn = await g.peerFound
defer: await peerConn.closeWithEof()
await g.mainLoop(peerConn)
let
game = Game.new()
netFut = networking(game)
nico.init("Status", "Tron")
nico.createWindow("Tron", mapSize * 4, mapSize * 4, 4, false)
nico.run(proc = discard, proc(dt: float32) = game.update(dt), proc = game.draw())
waitFor(netFut.cancelAndWait())
## And that's it! If you want to run this code locally, the simplest way is to use the
## first node as a boot node for the second one. But you can also use any rendezvous node