Generate packet Header from client

[Mr mr]

I'm trying to generate packets from client to send it to the server, and I'm stuck at the algorithm to generate the packet's header.
The following code works to generate packet's header at server-side:

var a = sequence[2] | sequence[3] << 8;

a ^= -(_mapleVersion + 1);
var b = a ^ length;

data[0] = a & 0xFF;

data[1] = (a >>> 8) & 0xFF;

data[2] = b & 0xFF;

data[3] = (b >>> 8) & 0xFF;

Sadly, this code doesn't work with client-side..
Browsing the source code of a packet sender by @Diamondo25, he currently have a different function to generate client and server headers, and his code to do the client-side is:

public byte[] getHeaderToServer(intsize)        {
    byte[] header = new byte[4];
    int a = IV[3] * 0x100 + IV[2];
    a = a ^ (_mapleVersion);
    int b = a ^ size;
    header[0] = Convert.ToByte(a % 0x100);
    header[1] = Convert.ToByte(a / 0x100);
    header[2] = Convert.ToByte(b % 0x100);
    header[3] = Convert.ToByte(b / 0x100);
    return header;

}

I tried to convert this to js, but didn't worked well.
How can this be done? (javascript)

 

[Diamondo25]

Oh man, using DPS tool i made years ago, which was based of MapleLib, is not the best source for this nowdays.
I think this is more related to what you are doing:

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