byte数组计算校验和,帧头长度为12

 

private boolean matchCrc(byte[] readData, int packLength, intindex) {

int total = 0;

int x = 0;

// 计算校验和,这里帧头长度为12

for (x = index + 12; x < index + 12 + packLength &&x < readData.length; x++) {

total += readData[x];

if (readData[x] < 0) {

// System.out.println(readData[x] + "<0");

total += 256;

}

}

if ((index + 13 + packLength) < readData.length) {

if (readData[index + 12 + packLength] == (byte) ((total &0xff00) >> 8)

&& (readData[index + 13 + packLength] == (byte) (total& 0xff))) {

return true;

}

}

return false;

}

1	2	3	4	5	6	7	8	9	10	11	12			23+3/43+3	24+3/44+3
数据包(11+字节)
帧头								IP地址		包长（数据长度）		数据		校验和
0x01	0xFF	0xFF	0xFF	0xFF	0xFF	0xFF	0xFF	高	低	--	--	……		--	--
										包长后加起