Server Sends Check To Client Tutorial

[JokeofWeek]

Alright, since I have often wondered about the potential dangers of people connecting with a different client to my game to hack it, I decided to come up with a way for the server to check whether the player was using a proper client.

Basically, what this does is sends a packet & a string to the client as an 'acknowledgment' packet and a string attached to it, to make sure the client isn't just sending back a wrong 'received' packet.

The server gives the client 15 seconds to reply (15 seconds for reasons such as lag, slower computers, etc.) and if isn't received, it boots the player!

So basically, add this to your AccountRec :

Code:

LoginTimer as double

In the local non-saved variables section.

In modConstants, add this :

Code:

Public Const ACK_KEY as String = "6594sdfsd9r3"

REMEBMER TO CHANGE THE KEY TO YOUR OWN!

Add this to the ClearPlayer sub :

Code:

Player(index).LoginTimer = 0

Now, in modGeneral, in the GameAI Sub add this :

Optimization Tip : Add the High Index to speed up the loop

Code:

For i = 1 To MAX_PLAYERS
        If GetTickCountNew > (Player(i).LoginTimer + 15000) And Player(i).LoginTimer  0 And Player(i).Login  "" Then
            Call HackingAttempt(i, "Invalid Client!")
        End If
        
    Next i

Now, in modHandleData, in sub HandleData, add this anywhere (preferably near the top) :

Code:

' :::::::::::::::::::::::::::::::::::
    ' :: Acknowledge has been received ::
    ' :::::::::::::::::::::::::::::::::::
    If LCase$(Parse(0)) = "ackrc" Then
        if trim(parse(1))  ACK_KEY then
            Call HackingAttempt(i, "Invalid Client!")
            Exit Sub
        end if
        Player(index).LoginTimer = 0
        Exit Sub
    End If

As you can see, this checks to make sure you got the right key, if not invalids you. Now, look for the "login" packet, and near the end of the if case, right under :

Code:

Call SendChars(index)

Add this :

Code:

' Show the player up on the socket status
            Call SendDataTo(index, "ackps" & SEP_CHAR & ACK_KEY & SEP_CHAR & END_CHAR)
            Player(index).LoginTimer = GetTickCount

Now, that's it for the server code! Very simple code on the client side. Near the top of sub HandleData, just add this :

Code:

' ::::::::::::::::::::::::
    ' :: Acknowledge Packet ::
    ' ::::::::::::::::::::::::
    If LCase(Parse(0)) = "ackps" Then
        Call SendData("ackrc" & SEP_CHAR & trim(parse(1)) & SEP_CHAR & END_CHAR)
        Exit Sub
    End If

And there you go Should work perfectly ^_^ If you have any questions or comments, just say/ask