int main() {
    ConnectTCP();
    LoadModbusFunctions();
    ModbusStack_Init( MODBUS_TCP, sendModbusMessage, recvModbusMessage, currentTime);
    ModbusStack_SetSlaveId( MODBUS_SLAVE_ADDRESS );
    ModbusStack_RegisterGetValue(getModbusValue);
    for(;;) {
       ModbusStack_Loop();
    }
}

bool getModbusValue(const unsigned char slaveAddress, const unsigned char function,
                    const unsigned short startingAddress, const unsigned short length,
                    unsigned char *data, const unsigned short maxPayloadSize,
                    unsigned char *errorCode)
{
    if( slaveAddress == MODBUS_SLAVE_ADDRESS && function == MODBUS_FUNCTION_03_READ_HOLDING_REGISTERS ) {
        memcpy(data, databaseHoldingRegisters + startingAddress, length * sizeof(short));
        return true ;
    }
    return false;
}

void sendModbusMessage(...) {...};
void recvModbusMessage(...) {...};
void currentTime(...) {...};