UDPRecv

[FrashMX]

Im having a problem with the UDPRecv function. I send a query to a server and the server replies only the part before the first space (hex character 20) of the packet. For some reason it does not parse the part after it. The packet sniffer does show the entire packet, so it's clearly something that goes wrong with UDPRecv here.

Is anyone experiencing something similar?

Regards,

- FMX

[seandisanti]

Im having a problem with the UDPRecv function. I send a query to a server and the server replies only the part before the first space (hex character 20) of the packet. For some reason it does not parse the part after it. The packet sniffer does show the entire packet, so it's clearly something that goes wrong with UDPRecv here.

Is anyone experiencing something similar?

Regards,

- FMX

<{POST_SNAPBACK}>

i actually haven't played with this at all, but think i will now that i know it's there and i'll let you know if i see similar issues.

[FrashMX]

IThankYou :]

[/dev/null]

Im having a problem with the UDPRecv function. I send a query to a server and the server replies only the part before the first space (hex character 20) of the packet. For some reason it does not parse the part after it. The packet sniffer does show the entire packet, so it's clearly something that goes wrong with UDPRecv here.

Is anyone experiencing something similar?

code would help.

Cheers

Kurt

[FrashMX]

Alright I got an update on the situation. It seems to be related to the handling of the NULL character in AutoIt. (Thanks dev)

Anyone has experience with this character?

Edited August 10, 2005 by FrashMX

[seandisanti]

Alright I get an update on the situation. It seems to be related to the handling of the NULL character in AutoIt. (Thanks dev)

Anyone has experience with this character?

<{POST_SNAPBACK}>

as he pointed out, your source would be very helpful in recreating the error and troubleshooting...

[FrashMX]

You're right. The script is for querying a gameserver.

I set up a random one in the script.

#include <string.au3>
#include <array.au3>

UDPStartup()

$socket = UDPOpen("82.133.85.17", 27025)
If @error <> 0 Then Exit

$infostring = "\xFF\xFF\xFF\xFF\x54\x53\x6F\x75\x72\x63\x65\x20\x45\x6E\x67\x69\x6E\x65\x20\x51\x75\x65\x72\x79\x00"

    UDPSend($socket, _HexToString($infostring))
    sleep(200)
    $data = UDPRecv($socket, 200)
   
    If $data <> "" Then
        MsgBox(0, "Query results", $data)
    EndIf
    Sleep(100)

Func OnAutoItExit()
    UDPCloseSocket($socket)
    UDPShutdown()
EndFunc

The output AutoIt gives:

ÿÿÿÿIjolt.co.uk - (14) CSS - cs_assault Only

Here the sniffer data, which shows there is more than just the part before the NULL char.

FF FF FF FF 49 07 6A 6F 6C 74 2E 63 6F 2E 75 6B  ....I.jolt.co.uk
20 2D 20 28 31 34 29 20 43 53 53 20 2D 20 63 73   - (14) CSS - cs
5F 61 73 73 61 75 6C 74 20 4F 6E 6C 79 00 63 73  _assault Only.cs
5F 61 73 73 61 75 6C 74 00 63 73 74 72 69 6B 65  _assault.cstrike
00 43 6F 75 6E 74 65 72 2D 53 74 72 69 6B 65 3A  .Counter-Strike:
20 53 6F 75 72 63 65 00 F0 00 0F 10 00 64 6C 00   Source......dl.
01 31 2E 30 2E 30 2E 32 32 00                   .1.0.0.22.

Edited August 10, 2005 by FrashMX

[seandisanti]

You're right. The script is for querying a gameserver.

I set up a random one in the script.

#include <string.au3>
#include <array.au3>

UDPStartup()

$socket = UDPOpen("82.133.85.17", 27025)
If @error <> 0 Then Exit

$infostring = "\xFF\xFF\xFF\xFF\x54\x53\x6F\x75\x72\x63\x65\x20\x45\x6E\x67\x69\x6E\x65\x20\x51\x75\x65\x72\x79\x00"

    UDPSend($socket, _HexToString($infostring))
    sleep(200)
    $data = UDPRecv($socket, 200)
   
    If $data <> "" Then
        MsgBox(0, "Query results", $data)
    EndIf
    Sleep(100)

Func OnAutoItExit()
    UDPCloseSocket($socket)
    UDPShutdown()
EndFunc

The output AutoIt gives:

ÿÿÿÿIjolt.co.uk - (14) CSS - cs_assault Only

Here the sniffer data, which shows there is more than just the part before the NULL char.

FF FF FF FF 49 07 6A 6F 6C 74 2E 63 6F 2E 75 6B  ....I.jolt.co.uk
20 2D 20 28 31 34 29 20 43 53 53 20 2D 20 63 73   - (14) CSS - cs
5F 61 73 73 61 75 6C 74 20 4F 6E 6C 79 00 63 73  _assault Only.cs
5F 61 73 73 61 75 6C 74 00 63 73 74 72 69 6B 65  _assault.cstrike
00 43 6F 75 6E 74 65 72 2D 53 74 72 69 6B 65 3A  .Counter-Strike:
20 53 6F 75 72 63 65 00 F0 00 0F 10 00 64 6C 00   Source......dl.
01 31 2E 30 2E 30 2E 32 32 00                    .1.0.0.22.

<{POST_SNAPBACK}>

it seems like it's just seeing it as a null terminated string... logical assumption usually, but not here i guess. one thing you could do is make a second (or more if there is more than one null in the string you're trying to receive) variable, $data2 or something that is assigned a value right after $data, it should pick up the next section after the null (or the null in which case you'd have to make a third to catch the next part probably) and then concatenate them, and work with that string as the full string...

[seandisanti]

it seems like it's just seeing it as a null terminated string... logical assumption usually, but not here i guess. one thing you could do is make a second (or more if there is more than one null in the string you're trying to receive) variable, $data2 or something that is assigned a value right after $data, it should pick up the next section after the null (or the null in which case you'd have to make a third to catch the next part probably) and then concatenate them,  and work with that string as the full string...

<{POST_SNAPBACK}>

Valik says pertinent stuff maybe that helps? granted he's talking about reading from a file, but essentially reading is reading... i still think my solution would work...

[FrashMX]

Well I dropped Larry a PM asking if he could add a switch to UDPRecv/TCPRecv to receive the data in hex. In that case the problem wouldn't be there

Any idea how I would assign a second variable to the stuff after the NULL char?

[seandisanti]

Any idea how I would assign a second variable to the stuff after the NULL char?

<{POST_SNAPBACK}>

sure thing, here's some slightly modified code...

#include <string.au3>
#include <array.au3>

UDPStartup()

$socket = UDPOpen("82.133.85.17", 27025)
If @error <> 0 Then Exit

$infostring = "\xFF\xFF\xFF\xFF\x54\x53\x6F\x75\x72\x63\x65\x20\x45\x6E\x67\x69\x6E\x65\x20\x51\x75\x65\x72\x79\x00"

    UDPSend($socket, _HexToString($infostring))
    sleep(200)
    $data = UDPRecv($socket, 200)
    $data2 = UDPRecv($socket, 200-StringLen($data))
    $data = $data & $data2    
If $data <> "" Then
        MsgBox(0, "Query results", $data)
    EndIf
    Sleep(100)

Func OnAutoItExit()
    UDPCloseSocket($socket)
    UDPShutdown()
EndFunc

all it's doing is another read, then concatenating the strings, nothing too spectacular... lemme know if that gets what you want it to

***edit***

had tried to bold some code, didn't work out, this is all i added:

$data2 = UDPRecv($socket, 200-StringLen($data))
    $data = $data & $data2

Edited August 11, 2005 by cameronsdad

[FrashMX]

Doesn't seem to work somehow. Thanks alot for trying though.

[/dev/null]

Doesn't seem to work somehow. Thanks alot for trying though.

<{POST_SNAPBACK}>

It can't work, as there is a NULL char in the string. This is an "end of string" marker in C and C++. Every function that relies on the standard C/C++ libs will stop further reading the string as soon as the first NULL char appears. Unfortunately there is nothing you can do about it.

Cheers

Kurt

[seandisanti]

It can't work, as there is a NULL char in the string. This is an "end of string" marker in C and C++. Every function that relies on the standard C/C++ libs will stop further reading the string as soon as the first NULL char appears. Unfortunately there is nothing you can do about it.

Cheers

Kurt

<{POST_SNAPBACK}>

right, so the null is caught in the attempt to readin in $data, then $data2 should get the rest, or if not, then $data2 should capture the null right? so a $data3 should be able to get the rest of the string until the next null right? maybe change

$data = UDPRecv($socket, 200)
$data2 = UDPRecv($socket, 200-StringLen($data))
$data = $data & $data2

to read

[code]
$data = UDPRecv($socket, 200)
$data2 = UDPRecv($socket,1)
$data3 = UDPRecv($socket, 200- (StringLen($data) +1))
$data = $data & $data3

[FrashMX]

Hm Larry have you been able to read my PM about this yet btw?

[seandisanti]

As AutoIt does not support binary data,,, u outta luck... try

UDPRecv($socket, 1)

and build your string a character at a time... poor speed , but theoretically possible...

Lar.

<{POST_SNAPBACK}>

wouldn't adding the UDPRecv($socket, 1) after the truncated string to absorb the null, then grabbing the next set (as in my example) effectively do the same thing if it's just a single string with a single Null in it? And as this is coming in as an automatic response, seems like the appearance of nulls in the string would be at regular intervals, or atleast have a set frequency, meaning if there is only one null in the string he wants this time, there should not be 2 in the same string next time right?

[Joshu]

Hey guys,

Just been screwing around with querying Source servers myself, Frash's query string set me on the right path for doing it - thanks man.

I know it's a few years late, but here's how you can work around the null characters in the string:

$data = UDPRecv($socket, 1024)
$dataarray = StringSplit($data, Chr(0))

If $data <> "" Then
    $reply_servername = StringMid($dataarray[1],7)
    $reply_map = $dataarray[2]
    $reply_game = $dataarray[4]
    $reply_players = Asc(StringMid($dataarray[6],1,1))
    $reply_maxplayers = Asc(StringMid($dataarray[6],2,1))
Else
    'no response from server
EndIf

Hope this helps someone.

Edited February 26, 2007 by Joshu