nios udp connection, can send but not receieve

hi, all. almost crazy about the udp connection based on development board, my code as follows, it can send message to the pc and pc can receieve the message without any problem, in my code, i run the pc as server and board as client. when pc receieve message, it will send it back to the board, however, my board never receieve it although i see the lan port receieveing flash, please suggest the reason

nios side

static void udp_test_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p,

struct ip_addr *addr, u16_t port)

{

err_t err;

err=udp_connect(pcb,addr,port);

if (err!= ERR_OK)

{

printf("\n ERROR connection in receieving %d \n",err);

}

udp_packets++;

udp_send(pcb,p);

pbuf_free(p);

udp_remove(pcb);

return;

}

void main()

{

int i;

struct udp_pcb *pcb;

struct pbuf* pbuflfsr;

struct ip_addr udpDestIpAddr,udpLocalIpAddr;

pbuf_layer layer=PBUF_TRANSPORT;

pbuf_flag flag=PBUF_RAM;

u16_t size=1024;

IP4_ADDR(&udpDestIpAddr, 10, 0, 0, 52);

IP4_ADDR(&udpLocalIpAddr, 10, 0, 0, 51);

printf("udp_init\n");

udp_packets = 0;

while(1)

{

pcb = udp_new();

udp_connect(pcb, &udpDestIpAddr,10);

pbuflfsr = pbuf_alloc(layer,size,flag);

for(i=0;i<=size-1;i++) //data

{

((u8_t *)(pbuflfsr->payload))[i] = 0x11;

}

udp_sendto(pcb, pbuflfsr, &udpDestIpAddr, 10);

usleep(500);

udp_recv(pcb,udp_test_recv,NULL);

pbuf_free(pbuflfsr);

udp_remove(pcb);

}

}

pc side:

SOCKET socket1;

struct sockaddr_in local;

struct sockaddr_in from;

int fromlen =sizeof(from);

local.sin_family=AF_INET;

local.sin_port=htons(10);

local.sin_addr.s_addr=INADDR_ANY;

socket1=socket(AF_INET,SOCK_DGRAM,0);

bind(socket1,(struct sockaddr*)&local,sizeof local);

while (1)

{

char buffer[1024]="\0";

printf("waiting for message from others-------------\n");

if (recvfrom(socket1,buffer,sizeof buffer,0,(struct sockaddr*)&from,&fromlen)!=SOCKET_ERROR)

{

sendto(socket1,buffer,sizeof buffer,0,(struct sockaddr*)&from,fromlen);

}

Sleep(5);

}

closesocket(socket1);