picker =[[GKPeerPickerController alloc] init];
    picker.delegate = self;
    picker.connectionTypesMask = GKPeerPickerConnectionTypeNearby;//设置成蓝牙的选择（另外一种是ONline的）    
    [picker show];

    [self.currentSession disconnectFromAllPeers];
    currentSession = nil;

    NSData *data;
    NSString *str = [NSString stringWithString:textField.text];
    data = [str dataUsingEncoding:NSASCIIStringEncoding];
    
    if (currentSession) {
        [self.currentSession sendDataToAllPeers:data withDataMode:GKSendDataReliable error:nil];
    }

#pragma mark  - Delegate
//设备连接时
- (void) peerPickerController:(GKPeerPickerController *)picker didConnectPeer:(NSString *)peerID toSession:(GKSession *)session{
    self.currentSession =session;//取得session对象
    session.delegate = self;
    [session setDataReceiveHandler:self withContext:nil];
    picker.delegate = nil;
    [picker dismiss];
}
//取消蓝牙选择器
-(void) peerPickerControllerDidCancel:(GKPeerPickerController *)picker{
    picker.delegate = nil;
}
//设备断开连接
- (void) session:(GKSession *)session peer:(NSString *)peerID didChangeState:(GKPeerConnectionState)state{
    switch (state) {
        case GKPeerStateConnected:
            NSLog(@"connected");
            break;
        case GKPeerStateDisconnected:
            NSLog(@"disconnected");
            currentSession = nil;
        default:
            break;
    }
}
//接受数据
- (void) receiveData:(NSData *)data fromPeer:(NSString *)peer inSession: (GKSession *)session context:(void *)context
{
    NSString *str;
    str = [[NSString alloc]initWithData:data encoding:NSASCIIStringEncoding];
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Data received" message:str delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];
    [alert show];
}