Usage of socket in Android NDK and analysis of considerations

The whole process of using socket in Android NDK is divided into the following parts:
Part 1: create socket and bind IP and ports

#include <sys/select.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#define MAX_DATA_BUF_LEN 10240
int sd = INVALID_SOCKET;
sockaddr_in addr_org;  //  Sending end address 
sd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);  //  create socket
addr_org.sin_family = AF_INET;
addr_org.sin_addr.s_addr = inet_addr("192.128.0.1");  //  The sender IP
addr_org.sin_port = htons(8080);  //  Sending end port 
bind(sd, (struct sockaddr *)&(addr_org), sizeof(struct sockaddr_in));  //  The binding IP And port 

Part 2: send data

sockaddr_in addr_dst;  //  Receiver address 
addr_dst.sin_family = AF_INET;
addr_dst.sin_addr.s_addr = inet_addr("192.128.0.2");  //  The receiving end IP
addr_dst.sin_port = htons(8080);  //  Receiver port 
... //  Generate the data to be sent to SendDataBuff,  Length of ulLen
sendto(sd, SendDataBuff, ulLen, 0, (struct sockaddr *)&(addr_dst), sizeof(sockaddr_in));  //  send SendDataBuff The data in the 

Part 3: receiving data in a thread (non-blocking)

void *SocketReceiveThread(void *pParam)
{
    fd_set fdset;
    struct timeval delayval;
    unsigned long lRetVal;
    delayval.tv_sec  = 0;
    delayval.tv_usec = 5000;    /*5ms Time delay */
    while (!end_flag)
    {
        FD_ZERO(&fdset);
        FD_SET(sd, &fdset);
        lRetVal = select(sd+1, &fdset, NULL, NULL, &delayval); //  Pay special attention to no 1 A parameter 
        if (0 == lRetVal)
        {
            continue;
        }
        else if (SOCKET_ERROR == lRetVal)
        {
            break;
        }
        else if (FD_ISSET(sd, &fdset) != 0)
        {
            char RecvDataBuff[MAX_DATA_BUF_LEN];  //  Receive data buffer
            unsigned long ulLen = recvfrom(sd, RecvDataBuff, MAX_DATA_BUF_LEN, 0, NULL, NULL);
            ... //  Process the received data 
        }
    }
}

Part 4: close socket
close(sd);