NSData *lengthData = [MessageDataPacketTool getsubdata:data withRange:NSMakeRange(0, 4)];
int length = 0;
[lengthData getBytes: &length length: sizeof(uint32_t)];
NTOHL(length);
IP_PACKET ipPacket;
ipPacket.length = length;

很明显这个length应该是错误的,也不清楚是什么原因