Tron example (#775)

Co-authored-by: lchenut <ludovic@status.im>

examples/tutorial_6_game.nim

@@ -0,0 +1,259 @@
+## # 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(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

libp2p.nim

@@ -17,7 +17,7 @@ when defined(nimdoc):
   ## stay backward compatible during the Major version, whereas private ones can
   ## change at each new Minor version.
   ##
-  ## If you're new to nim-libp2p, you can find a tutorial `here<https://github.com/status-im/nim-libp2p/blob/master/examples/tutorial_1_connect.md>`_
+  ## If you're new to nim-libp2p, you can find a tutorial `here<https://status-im.github.io/nim-libp2p/docs/tutorial_1_connect/>`_
   ## that can help you get started.
 
   # Import stuff for doc

libp2p.nimble

@@ -31,8 +31,8 @@ proc runTest(filename: string, verify: bool = true, sign: bool = true,
   exec excstr & " -r " & " tests/" & filename
   rmFile "tests/" & filename.toExe
 
-proc buildSample(filename: string, run = false) =
+proc buildSample(filename: string, run = false, extraFlags = "") =
-  var excstr = "nim c --opt:speed --threads:on -d:debug --verbosity:0 --hints:off -p:. "
+  var excstr = "nim c --opt:speed --threads:on -d:debug --verbosity:0 --hints:off -p:. " & extraFlags
   excstr.add(" examples/" & filename)
   exec excstr
   if run:
@@ -92,6 +92,7 @@ task website, "Build the website":
   tutorialToMd("examples/tutorial_3_protobuf.nim")
   tutorialToMd("examples/tutorial_4_gossipsub.nim")
   tutorialToMd("examples/tutorial_5_discovery.nim")
+  tutorialToMd("examples/tutorial_6_game.nim")
   tutorialToMd("examples/circuitrelay.nim")
   exec "mkdocs build"
 
@@ -106,6 +107,9 @@ task examples_build, "Build the samples":
     buildSample("tutorial_3_protobuf", true)
     buildSample("tutorial_4_gossipsub", true)
     buildSample("tutorial_5_discovery", true)
+    # Nico doesn't work in 1.2
+    exec "nimble install -y nico"
+    buildSample("tutorial_6_game", false, "--styleCheck:off")
 
 # pin system
 # while nimble lockfile

libp2p/discovery/discoverymngr.nim

@@ -89,10 +89,12 @@ method advertise*(self: DiscoveryInterface) {.async, base.} =
 
 type
   DiscoveryError* = object of LPError
+  DiscoveryFinished* = object of LPError
 
   DiscoveryQuery* = ref object
     attr: PeerAttributes
     peers: AsyncQueue[PeerAttributes]
+    finished: bool
     futs: seq[Future[void]]
 
   DiscoveryManager* = ref object
@@ -137,7 +139,22 @@ proc advertise*[T](dm: DiscoveryManager, value: T) =
   pa.add(value)
   dm.advertise(pa)
 
+template forEach*(query: DiscoveryQuery, code: untyped) =
+  ## Will execute `code` for each discovered peer. The
+  ## peer attritubtes are available through the variable
+  ## `peer`
+
+  proc forEachInternal(q: DiscoveryQuery) {.async.} =
+    while true:
+      let peer {.inject.} =
+        try: await q.getPeer()
+        except DiscoveryFinished: return
+      code
+
+  asyncSpawn forEachInternal(query)
+
 proc stop*(query: DiscoveryQuery) =
+  query.finished = true
   for r in query.futs:
     if not r.finished(): r.cancel()
 
@@ -158,6 +175,8 @@ proc getPeer*(query: DiscoveryQuery): Future[PeerAttributes] {.async.} =
     raise exc
 
   if not finished(getter):
+    if query.finished:
+      raise newException(DiscoveryFinished, "Discovery query stopped")
     # discovery loops only finish when they don't handle the query
     raise newException(DiscoveryError, "Unable to find any peer matching this request")
   return await getter

libp2p/multiaddress.nim

@@ -1084,6 +1084,9 @@ proc `$`*(pat: MaPattern): string =
   elif pat.operator == Eq:
     result = $pat.value
 
+proc bytes*(value: MultiAddress): seq[byte] =
+  value.data.buffer
+
 proc write*(pb: var ProtoBuffer, field: int, value: MultiAddress) {.inline.} =
   write(pb, field, value.data.buffer)
 

libp2p/peerinfo.nim

@@ -15,7 +15,7 @@ else:
 
 import std/[options, sequtils]
 import pkg/[chronos, chronicles, stew/results]
-import peerid, multiaddress, crypto/crypto, routing_record, errors, utility
+import peerid, multiaddress, multicodec, crypto/crypto, routing_record, errors, utility
 
 export peerid, multiaddress, crypto, routing_record, errors, results
 
@@ -69,6 +69,27 @@ proc update*(p: PeerInfo) {.async.} =
 proc addrs*(p: PeerInfo): seq[MultiAddress] =
   p.addrs
 
+proc fullAddrs*(p: PeerInfo): MaResult[seq[MultiAddress]] =
+  let peerIdPart = ? MultiAddress.init(multiCodec("p2p"), p.peerId.data)
+  var res: seq[MultiAddress]
+  for address in p.addrs:
+    res.add(? concat(address, peerIdPart))
+  ok(res)
+
+proc parseFullAddress*(ma: MultiAddress): MaResult[(PeerId, MultiAddress)] =
+  let p2pPart = ? ma[^1]
+  if ? p2pPart.protoCode != multiCodec("p2p"):
+    return err("Missing p2p part from multiaddress!")
+
+  let res = (
+    ? PeerId.init(? p2pPart.protoArgument()).orErr("invalid peerid"),
+    ? ma[0 .. ^2]
+  )
+  ok(res)
+
+proc parseFullAddress*(ma: string | seq[byte]): MaResult[(PeerId, MultiAddress)] =
+  parseFullAddress(? MultiAddress.init(ma))
+
 proc new*(
   p: typedesc[PeerInfo],
   key: PrivateKey,

mkdocs.yml

@@ -40,12 +40,13 @@ theme:
         name: Switch to light mode
 
 nav:
-  - Introduction: README.md
   - Tutorials:
+    - 'Introduction': README.md
     - 'Simple connection': tutorial_1_connect.md
     - 'Create a custom protocol': tutorial_2_customproto.md
     - 'Protobuf': tutorial_3_protobuf.md
     - 'GossipSub': tutorial_4_gossipsub.md
     - 'Discovery Manager': tutorial_5_discovery.md
+    - 'Game': tutorial_6_game.md
     - 'Circuit Relay': circuitrelay.md
   - Reference: '/nim-libp2p/master/libp2p.html'