_Games Programming with DirectPlay_
by Chris Howard

Figure 1. 

(a)

// NetRoids a64e8e40-5750-11cf-a4ac-0000c0ec0b9f
DEFINE_GUID(NETROIDS_GUID,0xa64e8e40,0x5750,0x11cf,
                              0xa4,0xac,0x00,0x00,
                              0xc0,0xec,0x0b,0x9f);

(b)

DirectPlayEnumerate(EnumSP, (LPVOID) hWndCtl);


Figure 2. 

// Create a new game, so we're the host
IsHost = TRUE;
// Initialize session description structure
memset(&dpDesc, 0x00, sizeof(DPSESSIONDESC));
dpDesc.dwSize = sizeof(dpDesc);
dpDesc.dwMaxPlayers = MAXPLAYERS;
dpDesc.dwFlags = DPOPEN_CREATESESSION;
dpDesc.guidSession = pGuid;
strcpy(dpDesc.szSessionName, FullName);
// Try to open the session
if ((hr = lpIDC->lpVtbl->Open(lpIDC, &dpDesc)) != DP_OK)
{
    // We failed
    lpIDC->lpVtbl->Release(lpIDC);
    lpIDC = NULL;
    return(FALSE);
}


Figure 3:

(a)

// Initialize the session description structure
memset(&dpDesc, 0x00, sizeof(DPSESSIONDESC));
dpDesc.dwSize = sizeof(dpDesc);
dpDesc.guidSession = *g_lpGuid;
// Enum sessions with 5 second timeout
lpIDC->lpVtbl->EnumSessions(lpIDC, &dpDesc, (DWORD)5000, EnumSession,
    (LPVOID) hWndCtl, (DWORD)NULL);


(b)

// Initialize session description struc to open it
memset(&dpDesc, 0x00, sizeof(DPSESSIONDESC));
dpDesc.dwSize       = sizeof(dpDesc);
dpDesc.guidSession  = *g_lpGuid;
dpDesc.dwFlags      = DPOPEN_OPENSESSION;
dpDesc.dwSession    = SendMessage((HWND) hWndCtl, LB_GETITEMDATA, iIndex, 0);
hr = lpIDC->lpVtbl->Open(lpIDC, &dpDesc);


(c)

// Either way, we have to create a player
if ((hr = lpIDC->lpVtbl->CreatePlayer(lpIDC, &dcoID, NickName,
    "NetRoids Player", &dphEvent)) != DP_OK)
{
    // We failed
    lpIDC->lpVtbl->Close(lpIDC);
    lpIDC->lpVtbl->Release(lpIDC);
    lpIDC = NULL;
    return(FALSE);
}


Figure 4. 

(a)

case MSG_HEREIAM:
    // Tell host we are here
    lpHereIAm = (LPHEREIAMMSG)CommBuff;
    lpHereIAm->MsgCode = msg;
    lpHereIAm->ID = (DWORD)dcoID;
    nBytes = sizeof(HEREIAMMSG);
    break;

(b)

// Send the message
lpIDC->lpVtbl->Send(lpIDC, dcoID, send_to, 0, (LPSTR) CommBuff, nBytes);


Figure 5. 


(a)

status = lpIDC->lpVtbl->Receive(lpIDC, &fromID, &dcoReceiveID,
    DPRECEIVE_ALL, CommBuff, &nBytes);

(b)

case MSG_HEREIAM:
    // Someone wants to play
    if (IsHost)
    {
        // I'm the host, so find out who is here
        lpHereIAm = (LPHEREIAMMSG)CommBuff;
        shipID = lpHereIAm->ID;
        // Initialize them
        SendGameMessage(MSG_INIT, shipID, 0);
    }
    break;