December 16th, 2004, 03:27 PM
Can anyone tell me if this is a valid statement.
s.send(chr(0xFF)+chr(BNETPacketId)+return struct.pack("< H", len(buffer)+4)+buffer)
I wasn't sure because it has +return, I just want to know if that will work correctly.
I also have another question, when using VB6 and you use the Left() function, if I do that (what python uses) would I always have to use - infront of my integer? Example,
Left(text1, 1). I forgot how to do it in VB6 but I think you get the idea. In Python would it be like, text1[-1]? I just need to know if I MUST use the - integer.
December 16th, 2004, 04:00 PM
x(...) calls a function and returns the result.
return is the command to send something out of a function as the result.
That would try to return exit the function you are in while also being in the middle of creating a string - Python will just complain and wont let you try to run it.
s.send("."+return struct.pack("< H", len(buffer)+4)+buffer)
If you just want "this string added to the result of this function" then you can do that:
s.send(chr(1) + chr(2) + struct.pack(...))
Nope. String/list slicing uses positive numbers to count from the left and negative characters to count from the right:
Positive numbers step in from the left.
Negative step in from the right.
Slicing can also do more than this, should you wish:
>>> text = "abcde"
>>> # take a single character
>>> text # from the left
>>> text # somewhere in the middle
>>> text[-1] # from the right
>>> # Take some characters
>>> text[1:] # from position 1 onwards - Right()
>>> text[:-1] # from the far left ending 1 from the right - ??
>>> text[:3] # from the left to position 3 - Left()
>>> text[-2:] # the last two characters
>>> text[2:4] # from position 2 to position 4 - Mid()
>>> text[2:-2] # starting 2 from the far left, ending 2 in from the far right
It's useful stuff, and far beats having named functions for each separate way of slicing a string up, IMHO.
>>> text[0:5:1] # from the left (0) to the right (5) in steps of 1
>>> text[0:5:2] # from 0 to 5 in steps of two
>>> text[::3] # from the left to the right in steps of three
>>> text[::-1] # well, try it and see.
Last edited by sfb; December 16th, 2004 at 04:18 PM.
December 16th, 2004, 04:42 PM
Ok, thanks I understand the second part much better now. I think I still have a problem with the first part however. In VB6 my code is, Winsock.SendData Chr(&HFF) & Chr(PacketId) & MakeWORD(Len(Buffer) + 4) & Buffer. In Python I have, s.send(chr(0xFF)+chr(BNETPacketId)+return struct.pack("< H", len(buffer)+4)+buffer). I'm not sure what you meant by what you said, but by doing +return struct.pack....... Will Python create some kind of an error? As of now it hasn't found anything wrong with it.
December 16th, 2004, 05:12 PM
What are you developing with? It does for me, in the interactive shell, in PythonWin's File -> Check, or when running Python script.py from the command line:
Originally Posted by †Yegg†
File "test1.py", line 1
s.send(chr(0xFF)+chr(BNETPacketId)+return struct.pack("< H", len(buffer)+4)+
SyntaxError: invalid syntax
December 16th, 2004, 06:29 PM
Ok, I've tried your way and I still got the invalid syntax error for the return function. Will my code function the same if I did the code in 2 lines? SOmething like,
data = 0x08 # this isn't 1 of the 2 lines
buffer = buffer+data
return struct.pack("< I", data)
Will this still work the same?
December 16th, 2004, 07:37 PM
I must admit I'm a bit lost... Let me explain the question as I am reading it and see if it makes any sense.
From what I can find on Google, MakeWORD "Combines two bytes to one 2-byte Word (aka Integer). e.g.
iRet = MakeWord(1, 1)"
Your call only has one argument to MakeWORD though, and that's the length of the buffer, so I assume it pads it to two bytes with zeros if necessary.
I guess that the data structure needed is:
- A single byte of value 0xFF
- A single byte Packet ID
- Two bytes (a word) for the length of the following data (+4)
- The buffer
In python this would likely become:
(Assuming BNETPacketId is an integer between 0 and 255)
socket.send(chr(0xFF) + chr(BNETPacketId) + struct.pack("<H", len(buffer) + 4) + buffer)
return doesn't really come into this bit at all...
data would become 0x08
buffer would become buffer + data
struct.pack would pad 0x08 into an unsigned long instead of an unsigned short
The function would exit, and the value from struct.pack would be returned to the caller.
Nothing would be sent anywhere and the changes just made to data and buffer would be lost.
So... it wouldn't do the same thing as I think your earlier code does.
I can see that you might mean something like this:
dataLength = struct.pack("<H", len(buffer)+4)
header = chr(0xFF) + chr(BNETPacketId) + datalength
message = header + buffer
sendResult = s.send(message)
December 16th, 2004, 07:51 PM
Ooooooo. I didn't realize I didn't need return in there. But thanks for all the help I think this cleared things up a lot for me. And you're right about the PacketId. Thanks.