Alef/nocdkey – User

nocdkey here doesn't mean you can play illegal copies with this plugin!

How to run 2 ArmA on the same PC

A fast way to setup MP missions is to run two ArmA games on the same computer. Let's call the first Editor and the second Client. Editor run the mission editor, selected clicking on Multiplayer -> New -> Edit/New. Client can now join it selecting Multiplayer -> LAN or Remote wiht IP 127.0.0.1. It will see Editor in edit mode. As Editor clicks on Preview to run the mission, a PBO named __cur_mp.pbo is create on the fly for Client to be downloaded. Both now enter the usual lobby and choose the slot they want. They play the mission, and when they leave back to the lobby, they can choose to run it again or go back. Editor in this case to the mission editor, Client to the multiplayer or Wait for host screen.

In order to avoid to click the menus, command line arguments are available.

For Editor

\ArmA\arma.exe  -host

For Client

\ArmA\arma.exe -connect=localhost

I like to suggest adding

-window -nosplash -world=empty -nopause

to speed up things and run safe from alt-tabbing.

Problems

All of this above should works if ArmA doesn't check for duplicated CD keys, and you have a single operative system user and a single installation of ArmA. You maybe know that there is an option in server.cfg called kickduplicate, which if set to 0 allows the same CD key to join a MP game. The problem is that server.cfg, or better, the file you provide with -config, is only read if you run ArmA with -server or the dedicated arma_server.exe or server on Linux. Because this check is done online at gamespy, if you drop your internet connection, the check isn't done. But this could be a problem, because while editing or testing, you usually want to search some forums or other online resources.

Solution

The CD key check will be skipped at least if the name for the gamespy servers are not found, or resolved. It doesn't simply mean you can force a different IP, like 127.0.0.1, editing your c:\windows\system32\drivers\etc\hosts.

ws2_32.dll

To connect to the Internet, like all the other programs on Windows, ArmA uses a DLL called ws2_32.dll, that is a file installed in c:\windows\system32. If you put another file with the same name in the ArmA installation directory, ArmA will use that instead of the Windows one. It is the same like Armalib from Kegetys, which uses dsound.dll to inject custom code in the ArmA process address space. I've modified a program found online (see the links below), that intercept the functions ArmA does to connect other computers. One of these functions is gethostbyname, which is used to obtain an internet address given a name, like www.ofpec.com returns 85.17.58.182. Now, if ArmA asks for hosts in gamespy.com domain, to check for duplicated CD keys, if the address it's found and valid, the check will happens. This function is enables only if you use -host and -nocdkey. The server will get the message "No challenge value was received from the master server." when attempting to check for duplicated CD keys. The DLL will intercept all of the network functions. All of them, apart the one above, add an overhead for this to work. This overhead consists of a single jmp instruction without stack management (nacked), which I suppose should at least be long as a single CPU cycle, or less. So if you run a 3GHz CPU, the added delay should be 0,33 ns (nanosecond, a billionth of second).

Legal

I suppose this is something legally doable, because BI already provided the way to work without checking for duplicated CD keys. If BI doesn't want this, I'll remove any reference to this work and notify the reachable forums and mirrors.

Links

• OFPEC beta request
• Xfire video showing a procure
• Original code: koaxia.com
• Original code: codeguru.com

Source

You get the full source in the distributed archive. This is the working code extracted from there:

struct hostent* FAR(__stdcall h_gethostbyname)(__in const char *name) {
    using namespace std;
    static const string master("armedass.master.gamespy.com"), available("armedass.available.gamespy.com");
    static const wstring mhost(L"-host"), mnocdkey(L"-nocdkey");
    static bool host=false, nocdkey=false, argschecked=false;
    struct hostent* FAR rc = 0;
    if (!argschecked) {
	argschecked=true;
	LPWSTR *szArglist;
	int nArgs;
	szArglist = CommandLineToArgvW(GetCommandLineW(), &nArgs);
	if( NULL != szArglist ) for(int i=0; i<nArgs ; ++i) {
		if (!host)    host=(mhost.compare(szArglist[i]) == 0); 
		if (!nocdkey) nocdkey=(mnocdkey.compare(szArglist[i]) == 0);
	}
	LocalFree(szArglist);
    }
    if (host && nocdkey && name && (master.compare(name) == 0 || available.compare(name) == 0) ) {
	p_WSASetLastError(WSAHOST_NOT_FOUND);
    } else {
	rc=p_gethostbyname(name);
    }
    return rc;
}

Where p_ is the original DLL function entry point and h_ the overloaded one.