help with this vb code pls?

[pattrick_george]

Hi there ,

I am looking in to a source code of yahoo messenger clone in vb6.0 , so obviously its winsock programming

so in The yahoo messenger header for yahoomessenger packet i see this declaration in the module,

YMSGPacket = "YMSG" & Chr(Int(Version / 256)) & Chr(Int(Version Mod 256)) & String(2, Chr(1)) & Chr(Int(Len(StrPacketType) / 256)) & Chr(Int(Len(StrPacketType) Mod 256)) & Chr(Int(StrComm / 256)) & Chr(Int(StrComm Mod 256)) & Mid(StrStat, 1, 4) & Mid(StrSession, 1, 4) & StrPacketType

tht code is the code which is sent through the winsock , I have a few more questions ,in what format is data senthrough winsockcomponent of visualbasic , string , hex ,binary or ascii

i see the mod 256 and / 256 code everywhere in this program , whats use of this statement

another code

TimSt = Chr$((((number And &HFF000000) / 256) / 256) / 256) & Chr$(((number And &HFF0000) / 256) / 256) & Chr$((number And &HFF00&) / 256) & Chr$(number And &HFF&)

every help would be greatly appreciated

thanks in advance

[techgnome]

/ 256 is simple division ... 1/4 = .25 4/2 = 2 ... etc.
mod 256 is a modulo operation, returns the remainder of a division... so 5 mod 3 is 2 4 mod 2 is 0 (2 goes into 4 evenly) 9 mod 3 is also 0, 11 mod 3 is 2 ...

-tg

[pattrick_george]

Thanks for the reply sir,ok , i know the operators division and mod,but in the case of this Chr(Int(Version / 256)

so my question is whats the use of dividing by 256 or getting mod 256 , is to convert string or integer in to one peculiar form

sorry i am a noob

[techgnome]

Looks like a form of data packing I think... but I'm not sure...

-tg

[DataMiser]

Everything has a use, why it is being done here I do not know.

In the case of CHR() and Mod 256 it would seem that the goal is to get a number < 256 and convert that to a character in the valid range of 0 - 255

Same with the division

[pattrick_george]

ok thanks to both of you , as i got this code from a yahoo clone project , is there a possibility that this is code is to convert it in to a form yahoo recognises or which is exclusive to yahoo

btw its a yahoo messenger clone

[LaVolpe]

ok thanks to both of you , as i got this code from a yahoo clone project , is there a possibility that this is code is to convert it in to a form yahoo recognises or which is exclusive to yahoo

A good assumption I would think.

Going back to dividing by 256 multiple times. Data packing, as suggeted, is probably the reason. You can pack quite a bit information in a Long value type (32 bits, 4 bytes). Take an IP address for example, written out: 255.255.255.255 would consist of 15 characters, at 1 byte per character, 15 bytes. A Long value is just 4 bytes. That same value as a Long would be simply negative one & displayed in hex as: FFFFFFFF (where FF = 255). Example: A Long value can contain 4 values, each in the range of 0-255. Each of the 4 "tokens" of that Long are offset by 256. Typically bit masking and integer division is used to extract the 4 bytes of a Long, not real division.

But to the point now. We can tell you what the code is doing from a logical perspective. However, why it is doing what it is doing is only known to the author and others that are familiar with the target's requirements; that of Yahoo