Note that this is just an idea. This code might not even compile, and you'd want to observe PTChannel disconnects & errors to remove or reset the _devices dict.

peertalk-multiple-devices-example.mm

@interface MyThing {
  NSMutableDictionary* _devices;
    // <NSNumber*deviceID>=<NSNull> while connecting
    // <NSNumber*deviceID>=<PTChannel> while connected
}

- (void)startListeningForDevices {
  NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];

  [nc addObserverForName:PTUSBDeviceDidAttachNotification object:PTUSBHub.sharedHub queue:nil usingBlock:^(NSNotification *note) {
    NSNumber* deviceID = [note.userInfo objectForKey:@"DeviceID"];
    NSLog(@"Device attached: %@", deviceID);
    _devices[deviceID] = [NSNull null];
    [self connectToDeviceWithDeviceID:deviceID];
  }];

  [nc addObserverForName:PTUSBDeviceDidDetachNotification object:PTUSBHub.sharedHub queue:nil usingBlock:^(NSNotification *note) {
    NSNumber *deviceID = [note.userInfo objectForKey:@"DeviceID"];
    NSLog(@"Device detached: %@", deviceID);
    PTChannel* chan = _devices[deviceID];
    [_devices removeObjectForKey:deviceID];
    if (![chan isKindOfClass:[NSNull class]]) {
      [chan close];
    }
  }];
}

- (void)connectToDeviceWithDeviceID:(NSNumber*)deviceID {
  const NSTimeInterval kDeviceReconnectDelay = 0.5;
  const int kMyThingTCPPortNumber = 1234;
  PTChannel *channel = [PTChannel channelWithDelegate:self];
  [channel connectToPort:kMyThingTCPPortNumber overUSBHub:PTUSBHub.sharedHub deviceID:deviceID callback:^(NSError *error) {
    if (error) {
      NSLog(@"Failed to connect to device #%@: %@", deviceID, error);
      if (_devices[deviceID]) {
        NSLog(@"Retrying connection to device #%@ in %f seconds", deviceID, kDeviceReconnectDelay);
        [self performSelector:_cmd withObject:deviceID afterDelay:kDeviceReconnectDelay];
      }
    } else {
      _devices[deviceID] = channel;
    }
  }];
}

- (void)forEachConnectedChannel:(void(^)(PTChannel* chan))fn {
  for (PTChannel* chan : _devices) {
    if (![chan isKindOfClass:[NSNull class]]) {
      fn(chan);
    }
  }
}

- (void)sendMessageToAllDevices:(NSString*)message {
  dispatch_data_t payload = PTExampleTextDispatchDataWithString(message);
  [self forEachConnectedChannel:^(PTChannel* chan) {
    [chan sendFrameOfType:PTExampleFrameTypeTextMessage tag:PTFrameNoTag withPayload:payload callback:^(NSError *error) {
      if (error) NSLog(@"Failed to send message: %@", error);
    }];
  }];
}

@end // MyThing