Because of the 8 peer limit I'm using NWListener, NWBrowser, NWConnection, and Bonjour for up to 20 peer-to-peer concurrent connections.
I followed this answer - https://developer.apple.com/forums/thread/652180 and this answer - https://developer.apple.com/forums/thread/661148 which are both from Apple engineers.
The first one said to create multiple concurrent NISessions:
All NISessions are peer-to-peer and as a result, creating multiple NISession objects is necessary to have multiple concurrent sessions. One approach is to create a dictionary between an identifier for the peer (i.e. a user identifier provided by your app MyAppUserID) and the NISession objects while also keeping track of the NIDiscoveryToken for each peer identifier: var sessions = [MyAppUserID: NISession]()
var peerTokensMapping = [NIDiscoveryToken: MyAppUserID]() And the second answer said to perform interactions with multiple iPhones:
Create an NISession for each peer you would like to interact with. For example, if you are interacting with two peers, create 2 * NISession objects. Each NISession will have a unique NIDiscoveryToken associated with it. Share discovery token #1 with peer #1, and share discovery token #2 with peer #2. When you receive discovery tokens from peers #1 and #2, create 2 * NINearbyPeerConfiguration objects and use them to run sessions #1 and #2, respectively. The problem is when sending out a NIDiscoveryToken via NWConnection, I can't find a way to link to the NISession from the sent out data to the token that is received from the incoming data after I initialize a NINearbyPeerConfiguration object:
eg.
User object which is sent and received when other devices are discovered
class User: NSObject, NSSecureCoding {
		var uid: String?
		var peerToken: NIDiscoveryToken? = nil
		init(uid: String, peerToken: NIDiscoveryToken) {...}
		// ... encoder for uid and peerToken
		// ... decoder for uid and peerToken
}
Send current user's NIDiscoveryToken data via NWBrowser and NWConnection and save it to the
peerTokensMapping dictionary and save the session to the sessionsArr
let currentUserId = "qwerty"
var sessionsArr = [NISession]()
var sessions = [String: NISession]()
var peerTokensMapping = [NIDiscoveryToken: String]()
func sendDataWhenNewDeviceIsDiscovered() {
		let session = NISession()
		session.delegate = self
		guard let myToken = session.discoveryToken else { return }
		let user = User(uid: currentUserId, peerToken: myToken)
		guard let outgoingData = try? NSKeyedArchiver.archivedData(withRootObject: user,
																														 requiringSecureCoding: true)
		else { return }
		let message = NWProtocolWebSocket.Metadata(opcode: .text)
		let context = NWConnection.ContentContext(identifier: "send", metadata: [message])
		connection.send(content: outgoingData, contentContext: context, isComplete: true, completion: .contentProcessed({ [weak self](error) in
		if let error = error { return }
				self?.sessionsArr.append(session)
				self?.peerTokensMapping[myToken] = self!.currentUserId
		print("Successfully Sent")
		}))
}
Receive other user's NIDiscoveryToken data via NWListener and NWConnection.
connection.receive(minimumIncompleteLength: 1, maximumLength: 65535) {
		[weak self](data, context, isComplete, error) in
		if let err = error { return }
		if let data = data, !data.isEmpty {
				self?.decodeReceived(data)
		}
}
func decodeReceived(_ data: Data) {
		guard let incomingData = try? NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data) as? User
		else { return }
		guard let uid = incomingData.uid, let peerToken = incomingData.peerToken
		else { return }
		let config = NINearbyPeerConfiguration(peerToken: peerToken)
		/* not sure what to do here to get the session that was created when the data was sent out */
		for (key,_) in peerTokensMapping {
				if key.??? == peerToken.??? {
						session.run(config)
						self.sessions[currentUserId] = session
						break
				}
		}
		/* or try this but this is the other user's peerToken so this will never work */
		for session in self.sessionsArr {
				if session.discoveryToken ?? "" == peerToken {
						session.run(config)
						self.sessions[currentUserId] = session
						break
				}
		}
}
Once the NINearbyPeerConfiguration is initialized how do I connect the incoming peerToken with the correct one that was sent out above that is currently inside the peerTokensMapping dict or the sessionsArr so that I can
get the session and call session.run(config)