Can't connect players in GameKit using GKMatchmaker.shared().findMatch - swift

Question

I'm trying to connect two players with each other using GameKit in a very simple game. I want to use GKMatchmaker.shared().findMatch as I don't want to show any GameCenter related view controllers. (to keep it simple)
Problem:
Even though GameKit creates a match after finding two players, an error occurs that prevents either player from sending any message to the others.
Current Situation:
The basic code is as follows (based on the docs described here: https://developer.apple.com/documentation/gamekit/finding_multiple_players_for_a_game)
print("Requesting multiplayer match")
let request = GKMatchRequest()
request.minPlayers = 2
request.maxPlayers = 2
request.recipientResponseHandler = {(player: GKPlayer, respnse: GKInviteRecipientResponse) -> Void in
print("new player about to join")
print(player.alias)
print(respnse)
}
GKMatchmaker.shared().findMatch(for: request, withCompletionHandler: {
(match: GKMatch?, error: Error?) -> Void in
if error != nil {
// Handle the error that occurred finding a match.
print("error during matchmaking")
print(error as Any)
} else if match != nil {
guard let match = match else { return }
print("connected to \(match.players.count) players")
// load the multiplayer data handler
let handler = MultiMatchHandler()
match.delegate = handler
// load the multiplayer service
let service = MultiMatchService(match: match)
service.sendMessageToAll(text: "Hello from the other side")
// finish the match making
GKMatchmaker.shared().finishMatchmaking(for: match)
// Start the game with the players in the match.
self.view?.presentScene(GameScene.newScene(multiplayer: service))
}
})
The output of that is
Requesting multiplayer match
2022-01-05 01:19:16.554959+0100 Grapefruit[38300:10026027] [Match] cannot set connecting state for players: (
"<GKPlayer: 0x282add280>(alias:... gamePlayerID:... teamPlayerID:... name:... status:(null) friendBiDirectional:0 friendPlayedWith:1 friendPlayedNearby:0 acceptedGameInviteFromThisFriend:0 initiatedGameInviteToThisFriend:0 automatchedTogether:1)"
), as there is no inviteDelegate set yet. The state might directly change to Ready when we set the inviteDelegate later and call sendQueuedStatesAndPackets.
2022-01-05 01:19:16.557002+0100 Grapefruit[38300:10026027] [Match] syncPlayers failed to loadPlayersForLegacyIdentifiers: (
"..."
)
connected to 0 players
sending text Hello from the other side failed
Findings:
minPlayers is set to 2. As the completion handler is called this means that at least one more player was found. But the number of players returned in match.players.count is 0
The matcher shows an error saying that cannot set connecting state for players ... as there is no inviteDelegate set yet. I can't find any info about this invite delegate.
Actual Question:
What is an inviteDelegate? Do I really need to implement such (if yes, then how?)? (I don't think so as the docs state that the match only starts after the invites are accepted).
How can I resolve this issue?

Answer 1

here is a working example for you. open on two machines, make sure both are authenticated, press "findMatch()" on both machines (and wait for confirmation), then ping baby ping
i believe the "no inviteDelegate set yet" error doesn't mean the match making necessary failed, and can safely be ignored, as mentioned here
you'll want to implement more of the GKMatchDelegate protocol, but this is a skeleton for demonstration purposes
import SwiftUI
import GameKit
import SpriteKit
class MyGameScene: SKScene, GKMatchDelegate {
override func didMove(to view: SKView) {
self.backgroundColor = .yellow
}
//GKMatchDelegate protocol
func match(_ match: GKMatch, didReceive data: Data, forRecipient recipient: GKPlayer, fromRemotePlayer player: GKPlayer) {
print("\(Self.self) \(#function) -- ping received")
}
}
struct Matchmaker: View {
#State var isAuthenticated:Bool = false
#State var scene = MyGameScene()
#State var match:GKMatch? = nil
var body: some View {
ZStack {
Color.clear
SpriteView(scene: scene)
VStack(alignment: .leading, spacing: 20) {
Text("1) authenticate() \(Image(systemName: isAuthenticated ? "checkmark.icloud" : "xmark.icloud"))")
Button { findMatch() } label: {
Text("2) findMatch() \(Image(systemName: (match != nil) ? "person.fill.checkmark" : "person.fill.xmark"))")
}
Button { ping() } label: {
Text("3) ping()")
}
}
}
.onAppear() {
authenticate()
}
}
func authenticate() {
GKLocalPlayer.local.authenticateHandler = { viewController, error in
if let error = error { print(error) }
isAuthenticated = (error == nil)
}
}
func findMatch() {
guard isAuthenticated else { return }
let request = GKMatchRequest()
request.minPlayers = 2
request.maxPlayers = 2
request.playerAttributes = 0xFFFFFFFF //mask for "i'll match with anyone"
GKMatchmaker.shared().findMatch (for: request) { match, error in
if let error = error { print(error) }
self.match = match
self.match?.delegate = scene
}
}
func ping() {
let players = match?.players ?? [];
let data = Data()
do {
try match?.send(data, to: players, dataMode: .reliable)
} catch {
print("Sending failed")
}
}
}