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计算机网络计算UDP校验和 · bigrandall.io
源IP地址：123.151.78.47(0x7b97, 0x4e2f)
目的IP地址：10.66.149.117(0xa42, 0x9575)
源端口：8000(0x1f40)
目的端口：4006(0xfa6)
UDP长度：39(0x27)
数据：0x023a, 0x2700, 0xcd27, 0x6784, 0xc57e, 0xf400, 0x0000, 0x5ad0, 0xc585, 0xf70f, 0xf03a, 0x71fa, 0x294d, 0xe354, 0x2bdf, 0x0300 校验和：0x9ab9
// C语言计算校验和 #include <stdio.h> unsigned short checksum ( unsigned short * buf , int nword ){ unsigned long sum; for (sum = 0 ;nword > 0 ;nword -- ){ sum += * buf ++ ; sum = (sum >> 16 ) +
(sum
&0x
ffff
);
}
return ~ sum;
}
int main (){
unsigned short buffer [ 26 ] = {
0x 7b97 , 0x 4e2f , // 源IP地址： 123.151.78.47(0x7b97, 0x4e2f)
0x 0a42 , 0x 9575 , // 目的IP地址：10.66.149.117(0xa42, 0x9575)
0x 0011 , 0x 0027 , // UDP协议字段值17(0x0011) UDP长度： 39(0x27)
0x 1f40 , 0x 0fa6 , // 源端口： 8000(0x1f40) 目的端口： 4006(0xfa6)
0x 0027 , 0x 0000 , // UDP长度： 39(0x27) 校验和（计算时置0）（0x0000）
0x 023a , 0x 2700 , // 数据字段，不够位数最后补0
0x cd27 , 0x 6784 ,
0x c57e , 0x f400 ,
0x 0000 , 0x 5ad0 ,
0x c585 , 0x f70f ,
0x f03a , 0x 71fa ,
0x 294d , 0x e354 ,
0x 2bdf , 0x 0300 };
int n = 26 ;
unsigned short re_checksum;
re_checksum = checksum (buffer,n);
printf ( " %x\t " ,re_checksum);
if (re_checksum == 0x 9ab9 )
printf ( "校验和正确! \n " );
else
printf ( "校验和不正确! \n " );
}
