The first thing, a Client has to do, is to send a login message:

//    Create a BMessage:
//    The command-type of the BMessage must be 0x87654321.
BMessage theMessage ( 0x87654321 );

//    Add the login fields to that message:
theMessage . AddString ( "Type", "login" );
theMessage . AddString ( "ClientName", "flintstone" );
theMessage . AddString ( "Password", "pentagon" );
theMessage . AddInt32 ( "Version", 1 );

//    Create a BMessenger:
status_t theStatus;
BMessenger theMessenger ( "application/x-vnd.EnemyTerritory.Server", -1, &theStatus );

//    Send the message:
//    the second parameter is the reply-handler.
//    Every message from the Server will be sent to this BHandler.
theMessenger . SendMessage ( & theMessage, be_app );
 

Then, your client will receive a welcome message from the server:

//    In your MessageReceived ( BMessage * theMessage ) function
//    you should test the command-type:
if ( theMessage -> what == 0x87654321 )
{

//    in this case, theMessage is a BMessage from the server.
//    test, if the message is a login - message:
if ( Equal ( theMessage -> FindString ( "Type" ), "welcome" ) )
{
//    Get the relevant data from the message:
theMessage -> FindInt32 ( "ClientID" );
theMessage -> FindInt32 ( "MapSize" );
};

Then, your client will receive status messages:

//    In your MessageReceived ( BMessage * theMessage ) function
//    you should test the command-type
//    and check, if this message is a status message:
if ( theMessage -> what == 0x87654321 )
if ( Equal ( theMessage -> FindString ( "Type" ), "status" ) )
{

BMessage includedMessage;

//    Get the map-fields from the message:
int theIndex = 0;
while ( theMessage -> FindMessage ( "Field", theIndex, & includedMessage ) >= B_NO_ERROR )
{

includedMessage . FindInt32 ( "Type" );
includedMessage . FindInt32 ( "XPos" );
includedMessage . FindInt32 ( "YPos" );
theIndex ++;
};

//    Get the objects from the message:
theIndex = 0;
while ( theMessage -> FindMessage ( "Object", theIndex, & includedMessage ) >= B_NO_ERROR )
{

includedMessage . FindInt32 ( "Type" );
includedMessage . FindInt32 ( "ID" );
includedMessage . FindInt32 ( "Owner" );
includedMessage . FindInt32 ( "XPos" );
includedMessage . FindInt32 ( "YPos" );
theIndex ++;
};

Your Client can make a move by sending the following BMessage:

//    Create the BMessage:
BMessage theMessage ( 0x87654321 );

//    Add the turn fields to that message:
theMessage . AddString ( "Type", "turn" );
theMessage . AddString ( "ClientName", "flintstone" );
theMessage . AddString ( "Password", "pentagon" );
theMessage . AddInt32 ( "ID", 17 );    //    replace the 17 by the objects ID!
theMessage . AddString ( "Action", "move" );
theMessage . AddInt32 ( "MoveToX", 17 );    //    replace the 17 by the new x-coordinate
theMessage . AddInt32 ( "MoveToY", 17 );    //    replace the 17 by the new y-coordinate

//    Create a BMessenger:
status_t theStatus;
BMessenger theMessenger ( "application/x-vnd.EnemyTerritory.Server", -1, &theStatus );

//    Send the message:
theMessenger . SendMessage ( & theMessage );