- (void)onSocket:(AsyncSocket *)sock didReadData:(NSData *)data withTag:(long)tag 
{ 
  while (_readBuf.length >= 10)//因為頭部固定10個字節(jié)，數(shù)據(jù)長度至少要大于10個字節(jié)，我們才能得到完整的消息描述信息 
  { 
    NSData *head = [_readBuf subdataWithRange:NSMakeRange(0, 10)];//取得頭部數(shù)據(jù) 
    NSData *lengthData = [head subdataWithRange:NSMakeRange(6, 4)];//取得長度數(shù)據(jù) 
    NSInteger length = [[[NSString alloc] initWithData:lengthData encoding:NSUTF8StringEncoding] integerValue];//得出內容長度 
    NSInteger complateDataLength = length + 10;//算出一個包完整的長度(內容長度＋頭長度) 
    if (_readBuf.length >= complateDataLength)//如果緩存中數(shù)據(jù)夠一個整包的長度 
    { 
      NSData *data = [_readBuf subdataWithRange:NSMakeRange(0, complateDataLength)];//截取一個包的長度(處理粘包) 
      [self handleTcpResponseData:data];//處理包數(shù)據(jù) 
      //從緩存中截掉處理完的數(shù)據(jù),繼續(xù)循環(huán) 
      _readBuf = [NSMutableData dataWithData:[_readBuf subdataWithRange:NSMakeRange(complateDataLength, _readBuf.length - complateDataLength)]]; 
    } 
    else//如果緩存中的數(shù)據(jù)長度不夠一個包的長度，則包不完整(處理半包，繼續(xù)讀取) 
    { 
      [_socket readDataWithTimeout:-1 buffer:_readBuf bufferOffset:_readBuf.length tag:0];//繼續(xù)讀取數(shù)據(jù) 
      return; 
    } 
  } 
  //緩存中數(shù)據(jù)都處理完了，繼續(xù)讀取新數(shù)據(jù) 
  [_socket readDataWithTimeout:-1 buffer:_readBuf bufferOffset:_readBuf.length tag:0];//繼續(xù)讀取數(shù)據(jù) 
}