The calculation method of UDP checksum

How to find the checksum of UDP, my IP is the 192.168.1.59 port number is 30002
The connected machine is the 192.168.1.179 port number is 30000

And then how do you find the checksum?

Reply to discussion (solution)

Goo ~ (???) B Don't understand

is chechsum how to get to, also have byte length? Do I need a byte length? Byte length If it is 66 then how to get to this checksum?

This is usually a system-level or network card to do, PHP is very difficult to do it?

Well, PHP is not a lot of this, and this checksum and transmission of data, all of the sum, and different or, and then summed. What But you don't know what to add?

Find a C code to transplant.

Find a C code to transplant.
There are no examples of what ah. Key PHP 16 in the number, is to first turn to binary, in order to make a different or sum?

PHP provides all the relevant functions
You put the part you don't have.

$FileData =array ();

8 byte header
$FileData [0]=0x75;
$FileData [1]=0x30;
$FileData [2]=0x75;
$FileData [3]=0x32;
$FileData [4]=0x00;
$FileData [5]=0x20;

------UDP Header Checksum




$a = $FileData [0]*256+ $FileData [1];
$b = $FileData [2]*256+ $FileData [3];
$c = $FileData [4]*256+ $FileData [5];
$d = ($a + $b + $c);

$FileData [6]=~ (($d >>8) &0xff);
$FileData [7]=~ ($d &0xff);
//---------------------

16 bytes of data
ID Number: 01020304
$FileData [8]=0x01;
$FileData [9]=0x02;
$FileData [10]=0x03;
$FileData [11]=0x04;

Action command: 0x00000001
$FileData [12]=0x00;
$FileData [13]=0x00;
$FileData [14]=0x00;
$FileData [15]=0x02;

Operation Result: 0x00000000
$FileData [16]=0x00;
$FileData [17]=0x00;
$FileData [18]=0x00;
$FileData [19]=0x01;

Keep
$FileData [20]=0x00;
$FileData [21]=0x00;
$FileData [22]=0x00;
$FileData [23]=0x00;

//---------------------
8-byte checksum
$FileData [24]= $FileData [0]^ $FileData [8]^ $FileData [16];
$FileData [25]= $FileData [1]^ $FileData [9]^ $FileData [17];
$FileData [26]= $FileData [2]^ $FileData [10]^ $FileData [18];
$FileData [27]= $FileData [3]^ $FileData [11]^ $FileData [19];
$FileData [28]= $FileData [4]^ $FileData [12]^ $FileData [20];
$FileData [29]= $FileData [5]^ $FileData [13]^ $FileData [21];
$FileData [30]= $FileData [6]^ $FileData [14]^ $FileData [22];
$FileData [31]= $FileData [7]^ $FileData [15]^ $FileData [23];

$arrayLen = sizeof ($FileData);
foreach ($FileData as $arr)
{
$str. = $arr;
}

Echo $str;
$str should be 16 bytes of data
Data content definition for UDP messages
Identification number Operation command operation data (result) retention
4 bytes 4 bytes 4 bytes 4 bytes


So now I want to get its checksum.

The checksum I wrote above is incorrect, and the output data is not correct.

PHP provides all the relevant functions
You put the part you don't have.

And how does IP turn into 16 binary? This is not the way,

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