How to know the short address of the node in the code?

1） If the node is in the association list, you can use

extern associated_devices_t *AssocGetWithExt( byte *extAddr );

2) if the node is not in the association list, you can use

afStatus_t ZDP_NwkAddrReq( uint8 *IEEEAddress, byte ReqType,
                           byte StartIndex, byte SecurityEnable )

Will I get the short address only?

1） It will return

typedef struct
{
  UINT16 shortAddr;                 // Short address of associated device
  uint16 addrIdx;                   // Index from the address manager
  byte nodeRelation;
  byte devStatus;                   // bitmap of various status values
  byte assocCnt;
  byte age;
  linkInfo_t linkInfo;
} associated_devices_t;

2）You will get the nwk addr response ， you can find

 the callback function

void ZDApp_ProcessMsgCBs( zdoIncomingMsg_t *inMsg )

Actually I am asking how to get the destination address of coordinator to send the light on/off status to Coordinator.

see the following code for reference...

afAddrType_t DstAddr

static void zclSampleLight_SendReport( void )
{
volatile ZStatus_t status;
afAddrType_t DstAddr;

//DstAddr.addr.extAddr = 0;
//DstAddr.addr.shortAddr = 0;
pzclSampleLight_ReportCmd->attrList[0].attrData = (uint8*)&zclSampleLight_OnOff;
zcl_SendReportCmd(SAMPLELIGHT_ENDPOINT,
&DstAddr,
ZCL_CLUSTER_ID_GEN_ON_OFF,
(zclReportCmd_t *)pzclSampleLight_ReportCmd,
1,0,1);

HalLcdWriteValue((uint32)(status), 10, 2);
}

Thanks 

the address of coordinator is always 0x0000

Why you need to get the coordinator address.