Getting Online with Multiplayer Gaming(16)

Getting Online with Multiplayer Gaming(16)

 

The Network Component

To use a client component, you have to derive a class from it and, in that derived
class, override the necessary functions. Those functions are few and are needed
only to convey when a connection to the server is achieved or to receive incoming
game messages.

To use the client network component, begin by deriving your own class from
cNetworkClient:

class  cClient :  public  cNetworkClient
{
private :
     virtual   bool  connect_complete( const  DPNMSG_CONNECT_COMPLETE* msg);
     virtual   bool  receive( const  DPNMSG_RECEIVE* msg);
};

To pass messages to the application, the derived application object needs only one
public function to siphon in received messages. Why only one? The client needs to
know when a connection is established to the server, which is the purpose of the
connect_complete function.

By using a global variable (g_connected) that represents the connection status, the
client network component can update the state of the connection as follows:

#define  CLIENT_WIDTH        640
#define  CLIENT_HEIGHT       480

#define  ACTION_MOVE_UP      1
#define  ACTION_MOVE_RIGHT   2
#define  ACTION_MOVE_DOWN    4
#define  ACTION_MOVE_LEFT    8
#define  ACTION_ATTACK       16

cApp*               g_app;
cNetworkAdapter*    g_adapter;

bool                 g_connected;

const   float  g_angles[13] = { 0.0f, 
                             0.0f, 1.57f, 0.785f, 3.14f,     
                             0.0f, 2.355f, 0.0f, 4.71f, 
                             5.495f, 0.0f, 0.0f, 3.925f };

/****************************************************************************************************/

bool  cClient::connect_complete( const  DPNMSG_CONNECT_COMPLETE* msg)
{
    g_connected = (msg->hResultCode == S_OK);
    g_app->set_local_player(msg->dpnidLocal);

     return   true ;
}

bool  cClient::receive( const  DPNMSG_RECEIVE* msg)
{
    g_app->receive(msg);

     return   true ;
}

/****************************************************************************************************/

void cApp::set_local_player(DPNID player_id)
{
EnterCriticalSection(&m_update_cs);

m_players[0].player_id = player_id;

LeaveCriticalSection(&m_update_cs);
}

Use the matching cApp::receive function for the cClient::receive function:

bool  cApp::receive( const  DPNMSG_RECEIVE* msg)
{
    sMsg* msg_ptr = (sMsg*) msg->pReceiveData;

     switch (msg_ptr->header.type)
    {
     case  MSG_GET_PLAYER_INFO:    // add  a player to list
     case  MSG_CREATE_PLAYER:
        create_player(msg_ptr);
         break ;

     case  MSG_DESTROY_PLAYER:     // remove a player from list
        destroy_player(msg_ptr);
         break ;

     case  MSG_STATE_CHANGE:       // change state of player
        change_player_state(msg_ptr);
         break ;
    }

     return   true ;
}

Notice that the receive function immediately processes incoming messages appropriately
by calling separate functions for each type of game message.