Why is Multipeer Connectivity so slow? - ios

Question

So, I have all multipeer connectivity related code in the main thread. I have a MCSession, MCNearbyServiceAdvertiser, and a MCNearbyServiceBrowser. These are all created with peerID, and I make sure only one sends an invitation.
The session becomes connected. My problems is that, two clients take around 20-30 seconds to connect. This is unacceptable. The clients are on good Wifi, and bluetooth. I want the browsing, invitation handler, and connection to take place within 1 second. Does anyone have any idea what is slowing things down?
Code is exactly as provided here and I also implemented certificateHandler(YES)
#interface SessionController () // Class extension
#property (nonatomic, strong) MCPeerID *peerID;
#property (nonatomic, strong) MCSession *session;
#property (nonatomic, strong) MCNearbyServiceAdvertiser *serviceAdvertiser;
#property (nonatomic, strong) MCNearbyServiceBrowser *serviceBrowser;
// Connected peers are stored in the MCSession
// Manually track connecting and disconnected peers
#property (nonatomic, strong) NSMutableOrderedSet *connectingPeersOrderedSet;
#property (nonatomic, strong) NSMutableOrderedSet *disconnectedPeersOrderedSet;
#end
#implementation SessionController
static NSString * const kMCSessionServiceType = #"mcsessionp2p";
#pragma mark - Initializer
- (instancetype)init
{
self = [super init];
if (self)
{
_peerID = [[MCPeerID alloc] initWithDisplayName:[[UIDevice currentDevice] name]];
_connectingPeersOrderedSet = [[NSMutableOrderedSet alloc] init];
_disconnectedPeersOrderedSet = [[NSMutableOrderedSet alloc] init];
NSNotificationCenter *defaultCenter = [NSNotificationCenter defaultCenter];
// Register for notifications
[defaultCenter addObserver:self
selector:#selector(startServices)
name:UIApplicationWillEnterForegroundNotification
object:nil];
[defaultCenter addObserver:self
selector:#selector(stopServices)
name:UIApplicationDidEnterBackgroundNotification
object:nil];
[self startServices];
_displayName = self.session.myPeerID.displayName;
}
return self;
}
#pragma mark - Memory management
- (void)dealloc
{
// Unregister for notifications on deallocation.
[[NSNotificationCenter defaultCenter] removeObserver:self];
// Nil out delegates
_session.delegate = nil;
_serviceAdvertiser.delegate = nil;
_serviceBrowser.delegate = nil;
}
#pragma mark - Override property accessors
- (NSArray *)connectedPeers
{
return self.session.connectedPeers;
}
- (NSArray *)connectingPeers
{
return [self.connectingPeersOrderedSet array];
}
- (NSArray *)disconnectedPeers
{
return [self.disconnectedPeersOrderedSet array];
}
#pragma mark - Private methods
- (void)setupSession
{
// Create the session that peers will be invited/join into.
_session = [[MCSession alloc] initWithPeer:self.peerID];
self.session.delegate = self;
// Create the service advertiser
_serviceAdvertiser = [[MCNearbyServiceAdvertiser alloc] initWithPeer:self.peerID
discoveryInfo:nil
serviceType:kMCSessionServiceType];
self.serviceAdvertiser.delegate = self;
// Create the service browser
_serviceBrowser = [[MCNearbyServiceBrowser alloc] initWithPeer:self.peerID
serviceType:kMCSessionServiceType];
self.serviceBrowser.delegate = self;
}
- (void)teardownSession
{
[self.session disconnect];
[self.connectingPeersOrderedSet removeAllObjects];
[self.disconnectedPeersOrderedSet removeAllObjects];
}
- (void)startServices
{
[self setupSession];
[self.serviceAdvertiser startAdvertisingPeer];
[self.serviceBrowser startBrowsingForPeers];
}
- (void)stopServices
{
[self.serviceBrowser stopBrowsingForPeers];
[self.serviceAdvertiser stopAdvertisingPeer];
[self teardownSession];
}
- (void)updateDelegate
{
[self.delegate sessionDidChangeState];
}
- (NSString *)stringForPeerConnectionState:(MCSessionState)state
{
switch (state) {
case MCSessionStateConnected:
return #"Connected";
case MCSessionStateConnecting:
return #"Connecting";
case MCSessionStateNotConnected:
return #"Not Connected";
}
}
#pragma mark - MCSessionDelegate protocol conformance
- (void)session:(MCSession *)session peer:(MCPeerID *)peerID didChangeState:(MCSessionState)state
{
NSLog(#"Peer [%#] changed state to %#", peerID.displayName, [self stringForPeerConnectionState:state]);
switch (state)
{
case MCSessionStateConnecting:
{
[self.connectingPeersOrderedSet addObject:peerID];
[self.disconnectedPeersOrderedSet removeObject:peerID];
break;
}
case MCSessionStateConnected:
{
[self.connectingPeersOrderedSet removeObject:peerID];
[self.disconnectedPeersOrderedSet removeObject:peerID];
break;
}
case MCSessionStateNotConnected:
{
[self.connectingPeersOrderedSet removeObject:peerID];
[self.disconnectedPeersOrderedSet addObject:peerID];
break;
}
}
[self updateDelegate];
}
- (void)session:(MCSession *)session didReceiveData:(NSData *)data fromPeer:(MCPeerID *)peerID
{
// Decode the incoming data to a UTF8 encoded string
NSString *receivedMessage = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(#"didReceiveData %# from %#", receivedMessage, peerID.displayName);
}
- (void)session:(MCSession *)session didStartReceivingResourceWithName:(NSString *)resourceName fromPeer:(MCPeerID *)peerID withProgress:(NSProgress *)progress
{
NSLog(#"didStartReceivingResourceWithName [%#] from %# with progress [%#]", resourceName, peerID.displayName, progress);
}
- (void)session:(MCSession *)session didFinishReceivingResourceWithName:(NSString *)resourceName fromPeer:(MCPeerID *)peerID atURL:(NSURL *)localURL withError:(NSError *)error
{
NSLog(#"didFinishReceivingResourceWithName [%#] from %#", resourceName, peerID.displayName);
// If error is not nil something went wrong
if (error)
{
NSLog(#"Error [%#] receiving resource from %# ", [error localizedDescription], peerID.displayName);
}
else
{
// No error so this is a completed transfer. The resources is located in a temporary location and should be copied to a permenant location immediately.
// Write to documents directory
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *copyPath = [NSString stringWithFormat:#"%#/%#", [paths firstObject], resourceName];
if (![[NSFileManager defaultManager] copyItemAtPath:[localURL path] toPath:copyPath error:nil])
{
NSLog(#"Error copying resource to documents directory");
}
else
{
// Get a URL for the path we just copied the resource to
NSURL *url = [NSURL fileURLWithPath:copyPath];
NSLog(#"url = %#", url);
}
}
}
// Streaming API not utilized in this sample code
- (void)session:(MCSession *)session didReceiveStream:(NSInputStream *)stream withName:(NSString *)streamName fromPeer:(MCPeerID *)peerID
{
NSLog(#"didReceiveStream %# from %#", streamName, peerID.displayName);
}
#pragma mark - MCNearbyServiceBrowserDelegate protocol conformance
// Found a nearby advertising peer
- (void)browser:(MCNearbyServiceBrowser *)browser foundPeer:(MCPeerID *)peerID withDiscoveryInfo:(NSDictionary *)info
{
NSString *remotePeerName = peerID.displayName;
NSLog(#"Browser found %#", remotePeerName);
MCPeerID *myPeerID = self.session.myPeerID;
BOOL shouldInvite = ([myPeerID.displayName compare:remotePeerName] == NSOrderedDescending);
if (shouldInvite)
{
NSLog(#"Inviting %#", remotePeerName);
[browser invitePeer:peerID toSession:self.session withContext:nil timeout:30.0];
}
else
{
NSLog(#"Not inviting %#", remotePeerName);
}
[self updateDelegate];
}
- (void)browser:(MCNearbyServiceBrowser *)browser lostPeer:(MCPeerID *)peerID
{
NSLog(#"lostPeer %#", peerID.displayName);
[self.connectingPeersOrderedSet removeObject:peerID];
[self.disconnectedPeersOrderedSet addObject:peerID];
[self updateDelegate];
}
- (void)browser:(MCNearbyServiceBrowser *)browser didNotStartBrowsingForPeers:(NSError *)error
{
NSLog(#"didNotStartBrowsingForPeers: %#", error);
}
#pragma mark - MCNearbyServiceAdvertiserDelegate protocol conformance
- (void)advertiser:(MCNearbyServiceAdvertiser *)advertiser didReceiveInvitationFromPeer:(MCPeerID *)peerID withContext:(NSData *)context invitationHandler:(void(^)(BOOL accept, MCSession *session))invitationHandler
{
NSLog(#"didReceiveInvitationFromPeer %#", peerID.displayName);
invitationHandler(YES, self.session);
[self.connectingPeersOrderedSet addObject:peerID];
[self.disconnectedPeersOrderedSet removeObject:peerID];
[self updateDelegate];
}
- (void)advertiser:(MCNearbyServiceAdvertiser *)advertiser didNotStartAdvertisingPeer:(NSError *)error
{
NSLog(#"didNotStartAdvertisingForPeers: %#", error);
}
#end

Answer 1

I've noticed this issue to and i can't seem to figure out whats happening here, it appears when debugging that there is a huge delay between the notification for state changing being fired, perhaps something to do with the view itself.
Update: Well i think i figured the issues out after a bit of reading, the response is pretty much instant now, in the notification in the view i have pushed the process back to the main thread like so:
-(void)peerDidChangeStateWithNotification:(NSNotification *)notification{
MCPeerID *peerID = [[notification userInfo] objectForKey:#"peerID"];
NSString *peerDisplayName = peerID.displayName;
MCSessionState state = [[[notification userInfo] objectForKey:#"state"] intValue];
if (state != MCSessionStateConnecting) {
if (state == MCSessionStateConnected) {
// add the user
[arrConnectedDevices addObject:peerDisplayName];
}
else if (state == MCSessionStateNotConnected){
// do we have connections
if ([arrConnectedDevices count] > 0) {
int indexOfPeer = [arrConnectedDevices indexOfObject:peerDisplayName];
[arrConnectedDevices removeObjectAtIndex:indexOfPeer];
}
}
}
// push to main queue for speedy response
dispatch_async(dispatch_get_main_queue(), ^(void) {
[collView reloadData];
BOOL peersExist = ([[appDelegate.mcManager.session connectedPeers] count] == 0);
NSLog(#"PEER COUNT IS %lu",(unsigned long)[[appDelegate.mcManager.session connectedPeers] count]);
[disconnectButton setEnabled:!peersExist];
if ([disconnectButton isEnabled]) {
[disconnectButton setBackgroundColor:[UIColor colorWithRed:(51/255.0) green:(202/255.0) blue:(168/255.0) alpha:1.0]];
}
else{
[disconnectButton setBackgroundColor:[UIColor colorWithRed:(107/255.0) green:(107/255.0) blue:(107/255.0) alpha:1.0]];
}
});
}
Hope this helps anyone who ran into the issues.