socket二进制报文

里面有帧头 字符串UTF-8  中间用0隔开  又一个字符串
byte[10]  byte[0]、byte[1]是帧头 0xaa,0x55
byte[2]-byte[5]是字符串utf-8  byte[6]=0,byte[7]-byte[9]是另外的字符串
这的一个包，该怎发？

NSMutableData *data = [[NSMutableData alloc] init];
    
    // 包头
    unsigned char header[] = { 0xAA, 0x55 };
    [data appendBytes:header length:sizeof(header)];
    
    // UTF8字符串
    NSString *string = @"我是UTF8";
    
    [data appendData:[string dataUsingEncoding:NSUTF8StringEncoding]];
    
    // 分隔符0x00
    unsigned char separator = 0;
    [data appendBytes:&separator length:1];
    
    NSString *otherString = @"其他UTF8";
    
    [data appendData:[otherString dataUsingEncoding:NSUTF8StringEncoding]];

typedef struct{
  u_int32_t first;
  u_int32_t second;
}pkt;

pkt t_pkt = {0};
pkt.first = 0xaa;

NSData *data = [NSData dataWithBytes:&t_pkt length:sizeof(t_pkt)];