这是大学计算机网络的一个课程设计：
//（（想要源代码或者有问题的小伙伴可以私聊我，我是拿js嵌html实现的，不用配置环境））
TCP校验和是一个端到端的校验和，由发送端计算，然后由接收端验证。其目的是为了发现TCP首部和数据在发送端到
接收端之间发生的任何改动。如果接收方检测到校验和有差错，则TCP段会被直接丢弃。
TCP校验和覆盖TCP首部和TCP数据，而IP首部中的校验和只覆盖IP的首部，不覆盖IP数据报中的任何数据。
TCP的校验和是必需的，而UDP的校验和是可选的。TCP和UDP计算校验和时，都要加上一个12字节的伪首部。
伪首部
伪首部共有12字节，包含如下信息：源IP地址、目的IP地址、保留字节(置0)、传输层协议号(TCP是6)、TCP报文长度(报头+数据)。
伪首部是为了增加TCP校验和的检错能力：如检查TCP报文是否收错了(目的IP地址)、传输层协议是否选对了(传输层协议号)等。
运行截图：
简单的算法实现如下：
<
script
type
=
“text/javascript”
>
// $(document).ready(function () {
// var ip = $(“#yuanip”).val();
// alert(ip);
// });
$
(
document
).
ready
(
function
() {
$
(
“#jiaoyan”
).
click
(
function
() {
//32网络地址数据部分取值转换
function
bitchange
(
number_1
,
number_2
) {
var
change
;
number_1
=
parseInt
(
number_1
,
10
);
number_2
=
parseInt
(
number_2
,
10
);
number_2
= (
“000000000”
+
number_2
.
toString
(
2
)).
substr
(-
8
);
change
=
number_1
.
toString
(
2
) +
number_2
;
change
=
parseInt
(
change
,
2
);
return
change
;
}
//tcp Data
function
addzero
(
tcp
) {
var
tcpdatasum
=
0
;
var
tcpsum
=
0
;
for
(
var
i
=
0
;
i
<
tcp
.
length
+
1
;
i
++) {
if
(
i
%
4
==
0
) {
tcpdatasum
=
parseInt
(
tcpdatasum
,
16
);
tcpsum
=
tcpsum
+
tcpdatasum
;
tcpdatasum
=
0
;
tcpdatasum
+=
tcp
.
charAt
(
i
);
}
else
{
tcpdatasum
+=
tcp
.
charAt
(
i
);
}
// tcpdatasum = (tcpdatasum + “0000”).substr(-4);
// tcpdatasum = parseInt(tcpdatasum,16);
// alert(tcpdatasum);
}
tcpdatasum
=
parseInt
(
tcpdatasum
,
16
);
tcpdatasum
=
tcpdatasum
.
toString
(
16
);
tcpdatasum
= (
tcpdatasum
+
“0000”
).
substr
(
0
,
4
);
tcpdatasum
=
parseInt
(
tcpdatasum
,
16
);
alert
(
tcpsum
+
tcpdatasum
);
return
tcpsum
+
tcpdatasum
;
}
//校验和计算并
function
checksum
(
sum
) {
sum
= (
sum
>>
16
) + (
sum
&
0xffff
);
sum
+= (
sum
>>
16
);
return
sum
;
}
//数组循环相加
function
getSum
() {
var
sum
=
0
;
for
(
var
i
=
0
;
i
<
data
.
length
;
i
++) {
sum
+=
parseInt
(
data
[
i
],
10
);
}
return
sum
;
}
//32bit change 16bit
function
bitchange_2
(
data
) {
var
n
=
0
;
var
n_1
=
“”
;
var
n_2
=
“”
;
data
=
parseInt
(
data
,
10
);
data
=
data
.
toString
(
2
);
data
= (
“00000000000000000000000000000000”
+
data
).
substr
(-
32
);
for
(
var
i
=
0
;
i
<
data
.
length
;
i
++) {
if
(
i
<
16
) {
n_1
+=
data
.
charAt
(
i
);
}
else
{
n_2
+=
data
.
charAt
(
i
);
}
}
n_1
=
parseInt
(
n_1
,
2
);
return
n_1
;
}
function
bitchange_3
(
data
) {
var
n
=
0
;
var
n_1
=
“”
;
var
n_2
=
“”
;
data
=
parseInt
(
data
,
10
);
data
=
data
.
toString
(
2
);
data
= (
“00000000000000000000000000000000”
+
data
).
substr
(-
32
);
for
(
var
i
=
0
;
i
<
data
.
length
;
i
++) {
if
(
i
<
16
) {
n_1
+=
data
.
charAt
(
i
);
}
else
{
n_2
+=
data
.
charAt
(
i
);
}
}
n_2
=
parseInt
(
n_2
,
2
);
return
n_2
;
}
//生成报文
function
baowen
() {
var
bw
=
“”
;
var
bw_1
=
“”
;
for
(
var
i
=
0
;
i
<
data
.
length
–
1
;
i
++) {
// sum += parseInt(data[i], 10);
// sum = checksum(sum);
data
[
i
] =
parseInt
(
data
[
i
],
10
);
data
[
i
] = (
“0000”
+
data
[
i
].
toString
(
16
)).
substr
(-
4
);
bw
=
bw
+
data
[
i
];
}
return
bw
+
sum
+
tcp
;
}
//报文字符串格式化
function
baowenzl
() {
var
bw_2
=
“”
;
for
(
var
i
=
0
;
i
<
a
.
length
;
i
++) {
if
(
i
%
2
!=
0
) {
bw_2
=
bw_2
+
a
.
charAt
(
i
) +
” ”
;
}
else
bw_2
=
bw_2
+
a
.
charAt
(
i
);
}
return
bw_2
;
}
var
data
=
new
Array
();
var
yuanip1
=
$
(
“#yuanip1”
).
val
();
var
yuanip2
=
$
(
“#yuanip2”
).
val
();
var
yuanip3
=
$
(
“#yuanip3”
).
val
();
var
yuanip4
=
$
(
“#yuanip4”
).
val
();
var
mudiip1
=
$
(
“#mudiip1”
).
val
();
var
mudiip2
=
$
(
“#mudiip2”
).
val
();
var
mudiip3
=
$
(
“#mudiip3”
).
val
();
var
mudiip4
=
$
(
“#mudiip4”
).
val
();
data
[
4
] =
$
(
“#xieyitype”
).
val
();
data
[
5
] =
$
(
“#tcplength”
).
val
();
data
[
6
] =
$
(
“#yuanport”
).
val
();
data
[
7
] =
$
(
“#mudiport”
).
val
();
var
bit32_1
=
$
(
“#number”
).
val
();
var
bit32_2
=
$
(
“#acknumber”
).
val
();
one
=
$
(
“#shift”
).
val
();
two
=
$
(
“#urg”
).
val
();
three
=
$
(
“#ack”
).
val
();
four
=
$
(
“#psh”
).
val
();
five
=
$
(
“#rst”
).
val
();
six
=
$
(
“#syn”
).
val
();
seven
=
$
(
“#fin”
).
val
();
data
[
13
] =
$
(
“#window”
).
val
();
// data[12] = $(“#finger”).val();
var
tcp
=
$
(
“#tcp”
).
val
();
data
[
0
] =
bitchange
(
yuanip1
,
yuanip2
);
data
[
1
] =
bitchange
(
yuanip3
,
yuanip4
);
data
[
2
] =
bitchange
(
mudiip1
,
mudiip2
);
data
[
3
] =
bitchange
(
mudiip3
,
mudiip4
);
//一堆乱七八糟的数据移位
data
[
5
] =
parseInt
(
data
[
5
],
10
) + (
tcp
.
length
/
2
) ;
$
(
“#tcplength”
).
val
(
data
[
5
]);
data
[
8
] =
bitchange_2
(
bit32_1
);
data
[
9
] =
bitchange_3
(
bit32_1
);
data
[
10
] =
bitchange_2
(
bit32_2
);
data
[
11
] =
bitchange_3
(
bit32_2
);
one
=
parseInt
(
one
,
10
);
one
=
one
.
toString
(
2
);
var
sum_5
=
one
+
“000000”
+
two
+
three
+
four
+
five
+
six
+
seven
;
sum_5
=
parseInt
(
sum_5
,
2
);
data
[
12
] =
sum_5
;
data
[
14
] =
addzero
(
tcp
);
// var wsum = parseInt(data[0],10) + parseInt(data[1],10) + parseInt(data[2],10) + parseInt(data[3],10) + parseInt(data[4],10) + parseInt(data[6],10) + parseInt(data[5],10);
// var sum = parseInt(data[5],10) + parseInt(data[7],10) + parseInt(data[8],10) + parseInt(data[9],10) + parseInt(data[10],10) + parseInt(data[11],10) + parseInt(data[12],10) + parseInt(data[13],10) + parseInt(data[14],10) + parseInt(data[15],10) + parseInt(data[16],10) + parseInt(data[17],10) + parseInt(data[18],10) + parseInt(data[19],10);
// var zsum = wsum +sum +parseInt(data[20],10);
var
sum
=
getSum
(
data
);
sum
=
checksum
(
sum
);
sum
=
parseInt
(
sum
,
10
);
sum
=
0xffff
–
sum
;
// var sum_2 = (“0000000000000000” + sum.toString(2)).substr(-16);
// var wsum = getSum();
// alert(wsum);
// alert(sum);
// alert(zsum);
// sum = checksum(zsum);
sum
=
sum
.
toString
(
16
);
$
(
“#checksum_1”
).
val
(
sum
);
// sum = parseInt(sum,10);
// sum = 0xffff-sum;
// sum = sum.toString(2);
// sum = (‘000000000000000’+sum).slice(-16);
// alert(sum);
var
a
=
baowen
(
data
);
a
=
baowenzl
(
a
);
$
(
“#jyprint”
).
val
(
a
);
});
});
<
/
script
>