static void socket_cb(SOCKET sock, uint8_t u8Msg, void *pvMsg)
{
    static uint8_t fsock = 0;
    static uint8_t rtsp_req[2];
    uint8_t argmint[1000];
    uint16_t argmintlen = 0;
    uint16_t i = 0;
    
    switch (u8Msg) {
    /* Socket bind */
    case SOCKET_MSG_BIND:
    {
        tstrSocketBindMsg *pstrBind = (tstrSocketBindMsg *)pvMsg;
        if (pstrBind && pstrBind->status == 0) {
            printf("socket_cb: bind success!\r\n");
            listen(tcp_server_socket, 0);
        } else {
            printf("socket_cb: bind error!\r\n");
            close(tcp_server_socket);
            tcp_server_socket = -1;
        }
    }
    break;

    /* Socket listen */
    case SOCKET_MSG_LISTEN:
    {
        tstrSocketListenMsg *pstrListen = (tstrSocketListenMsg *)pvMsg;
        if (pstrListen && pstrListen->status == 0) {
            printf("socket_cb: listen success!\r\n");
            accept(tcp_server_socket, NULL, NULL);
        } else {
            printf("socket_cb: listen error!\r\n");
            close(tcp_server_socket);
            tcp_server_socket = -1;
        }
    }
    break;

    /* Connect accept */
    case SOCKET_MSG_ACCEPT:
    {
        tstrSocketAcceptMsg *pstrAccept = (tstrSocketAcceptMsg *)pvMsg;
        if (pstrAccept) {
            //printf("socket_cb: Connect accept success! rtsp_req=%d\r\n",rtsp_req[0]);
            accept(tcp_server_socket, NULL, NULL);
            tcp_client_socket = pstrAccept->sock;
            recv(tcp_client_socket, gau8SocketTestBuffer, sizeof(gau8SocketTestBuffer), 0);
        } else {
            printf("socket_cb: accept error!\r\n");
            close(tcp_server_socket);
            tcp_server_socket = -1;
        }
    }
    break;

    /* Message send */
    case SOCKET_MSG_SEND:
    {
        if (fsock==1) //для OPTIONS нужно закрыть сокет, иначе не пошлется DESCRIBE
        {
            close(tcp_client_socket);
        }
        else    
            recv(tcp_client_socket, gau8SocketTestBuffer, sizeof(gau8SocketTestBuffer), 0);
        
            
    }
    break;

    /* Message receive */
    case SOCKET_MSG_RECV:
    {
        tstrSocketRecvMsg *pstrRecv = (tstrSocketRecvMsg *)pvMsg;
        
        //при поступлении нового сообщения, размер которого превышает 0 байт, разберем это сообщение и найдем в нем RTSP запросы
        if (pstrRecv && pstrRecv->s16BufferSize > 0)
        {
            argmintlen = rtsp_parse( pstrRecv, &argmint[0], &rtsp_req[0]);
            
            fsock++;
            send(tcp_client_socket, &argmint[0], argmintlen, 0);
                        
        }
        //иначе закрываем сокет
        else
        {
            printf("socket_cb: recv error!\r\n");
            close(tcp_server_socket);
            tcp_server_socket = -1;
        }
        
    }

    break;

    default:
        break;
    }
}

ret = nm_read_reg_with_ret(0x150400,(uint32 *)&dma_addr);

Все эти регистры не документированы и о них знать не положено. Все должно работать с предоставленным API.

-- WINC1500 UDP client example --
-- SAMD21_XPLAINED_PRO --
-- Compiled: Jun  2 2015 22:12:38 --
(APP)(INFO)Chip ID 1502b1(APP)(INFO)Firmware ver   : 18.1.1

(APP)(INFO)Min driver ver : 18.1.1

(APP)(INFO)Curr driver ver: 18.1.1wifi_cb: M2M_WIFI_RESP_CON_STATE_CHANGED: CONNECTED
wifi_cb: M2M_WIFI_REQ_DHCP_CONF : IP is 192.168.43.241
main: message sent
socket_cb: sendto success!
main: message sent
socket_cb: sendto success!
main: message sent
socket_cb: sendto success!
...
        вроде все норм, пакеты шлются (секунды 2)
....
main: message sent
socket_cb: sendto success!
ent
socket_cb: sendto success!
main: failed to send status report error! -14
...
      начинают пролетать ошибки (секунды 2)
...
main: message sent
socket_cb: sendto success!
main: message sent
socket_cb: sendto success!
main: message sent
socket_cb: sendto success!
main: failed to send status report error! -14

...

d status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
main: failed to send status report error! -14
...
      все - зациклился, постоянно выдает эту ошибку