iOS--(转)WiFi传输数据

什么是Multipeer Connectivity？
在iOS7中，引入了一个全新的框架——Multipeer Connectivity（多点连接）。利用Multipeer Connectivity框架，即使在没有连接到WiFi（WLAN）或移动网络（xG）的情况下，距离较近的Apple设备（iMac/iPad/iPhone）之间可基于蓝牙和WiFi（P2P WiFi）技术进行发现和连接实现近场通信。

Multipeer Connectivity扩充的功能与利用AirDrop传输文件非常类似，可以将其看作AirDrop不能直接使用的补偿，代价是需要自己实现。

本Demo主要用到4个类：

MCBrowserViewController:MCBrowserViewController继承自UIViewController，提供了基本的UI应用框架。

MCAdvertiserAssistant、MCAdvertiserAssistant为针对Advertiser封装的管理助手,主要处理广播信息。

MCSession:类似TCP链接中的socket。创建MCSession时，需指定自身MCPeerID，类似bind。

MCPeerID:类似sockaddr，用于标识连接的两端endpoint，通常是昵称或设备名称。

1、简单地建立一个界面，主要有连接和发送2个UIButton。
create_button.png

2、Multipeer Connectivity框架初始化这4个类。

pragma mark - Wifi Sharing Methods

-(void)setUpMultipeer
{
// Setup peer ID
self.myPeerID = [[MCPeerID alloc] initWithDisplayName:[UIDevice currentDevice].name];

//  Setup session
self.mySession = [[MCSession alloc] initWithPeer:self.myPeerID];
self.mySession.delegate = self;

//  Setup BrowserViewController
self.browserVC = [[MCBrowserViewController alloc] initWithServiceType:@"chat" session:self.mySession];
self.browserVC.delegate = self;

//  Setup Advertiser
self.advertiser = [[MCAdvertiserAssistant alloc] initWithServiceType:@"chat" discoveryInfo:nil session:self.mySession];
[self.advertiser start];

}

-(void)showBrowserVC
{
[self presentViewController:self.browserVC animated:YES completion:nil];
}

-(void)dismissBrowserVC
{
[self.browserVC dismissViewControllerAnimated:YES completion:^(void){
[self invokeAlertMethod:@"连接成功" Body:@"Both device connected successfully." Delegate:nil];
}];
}

-(void)stopWifiSharing:(BOOL)isClear
{
if(isClear && self.mySession != nil){
[self.mySession disconnect];

    [self.mySession setDelegate:nil];

    self.mySession = nil;

    self.browserVC = nil;
}

}
3、MCBrowserViewController代理方法

pragma marks MCBrowserViewControllerDelegate

// 点击完成
-(void)browserViewControllerDidFinish:(MCBrowserViewController *)browserViewController
{
[self dismissBrowserVC];
[marrReceiveData removeAllObjects];
}

// 点击取消
-(void)browserViewControllerWasCancelled:(MCBrowserViewController *)browserViewController
{
[self dismissBrowserVC];
}
4、MCSession代理方法
主要处理发送方传递的文件或者信息

// Received data from remote peer

• (void)session:(MCSession *)session didReceiveData:(NSData *)data fromPeer:(MCPeerID *)peerID
  {
  NSLog(@"data receiveddddd : %lu",(unsigned long)data.length);

  if (data.length > 0) {
  if (data.length < 2) {
  noOfDataSend++;
  NSLog(@"noofdatasend : %zd",noOfDataSend);
  NSLog(@"array count : %zd",marrFileData.count);
  if (noOfDataSend < ([marrFileData count])) {
  [self.mySession sendData:[marrFileData objectAtIndex:noOfDataSend] toPeers:[self.mySession connectedPeers] withMode:MCSessionSendDataReliable error:nil];
  }else {
  [self.mySession sendData:[@"File Transfer Done" dataUsingEncoding:NSUTF8StringEncoding] toPeers:[self.mySession connectedPeers] withMode:MCSessionSendDataReliable error:nil];
  }
  } else {
  if ([[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] isEqualToString:@"File Transfer Done"]) {
  [self appendFileData];
  }else {
  [self.mySession sendData:[@"1" dataUsingEncoding:NSUTF8StringEncoding] toPeers:[self.mySession connectedPeers] withMode:MCSessionSendDataReliable error:nil];
  [marrReceiveData addObject:data];
  }
  }
  }
  }

// Received a byte stream from remote peer

• (void)session:(MCSession *)session didReceiveStream:(NSInputStream *)stream withName:(NSString *)streamName fromPeer:(MCPeerID *)peerID
  {
  NSLog(@"did receive stream");
  }

// Start receiving a resource from remote peer

• (void)session:(MCSession *)session didStartReceivingResourceWithName:(NSString *)resourceName fromPeer:(MCPeerID *)peerID withProgress:(NSProgress *)progress
  {
  NSLog(@"start receiving");
  }

// Finished receiving a resource from remote peer and saved the content in a temporary location - the app is responsible for moving the file to a permanent location within its sandbox

• (void)session:(MCSession *)session didFinishReceivingResourceWithName:(NSString *)resourceName fromPeer:(MCPeerID *)peerID atURL:(NSURL *)localURL withError:(NSError *)error
  {
  NSLog(@"finish receiving resource");
  }

-(void)session:(MCSession *)session peer:(MCPeerID *)peerID didChangeState:(MCSessionState)state
{
NSLog(@"change state : %zd",state);
}
5、发送图片（此Demo只是简单地做了个收发图片的Demo，此框架可实现的功能当然不止这么简单。）
-(void)sendData
{
[marrFileData removeAllObjects];

NSData *sendData = UIImagePNGRepresentation([UIImage imageNamed:@"test2.png"]);
NSUInteger length = [sendData length];
NSUInteger chunkSize = 100 * 1024;
NSUInteger offset = 0;
do {
    NSUInteger thisChunkSize = length - offset > chunkSize ? chunkSize : length - offset;
    NSData* chunk = [NSData dataWithBytesNoCopy:(char *)[sendData bytes] + offset
                                         length:thisChunkSize
                                   freeWhenDone:NO];
    NSLog(@"chunk length : %lu",(unsigned long)chunk.length);

    [marrFileData addObject:[NSData dataWithData:chunk]];
    offset += thisChunkSize;
} while (offset < length);

noOfdata = [marrFileData count];
noOfDataSend = 0;

if ([marrFileData count] > 0) {
    [self.mySession sendData:[marrFileData objectAtIndex:noOfDataSend] toPeers:[self.mySession connectedPeers] withMode:MCSessionSendDataReliable error:nil];
}

}

-(void)appendFileData
{
NSMutableData *fileData = [NSMutableData data];

for (int i = 0; i < [marrReceiveData count]; i++) {
    [fileData appendData:[marrReceiveData objectAtIndex:i]];
}

[fileData writeToFile:[NSString stringWithFormat:@"%@/Image.png", [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"]] atomically:YES];

UIImageWriteToSavedPhotosAlbum([UIImage imageWithData:fileData], self, @selector(image:didFinishSavingWithError:contextInfo:), nil);

}

• (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo
  {
  if (!error) {
  [self invokeAlertMethod:@"发送成功" Body:@"图片已保存到手机相册" Delegate:nil];
  }
  }