UDP client on a OS X - sockets

Question

I wanted to compile sample code for a UDP client on a Mac OS X, but got a following error:
client.c:91:9: error: use of undeclared identifier 'MSG_CONFIRM'
MSG_CONFIRM, (const struct sockaddr *) &servaddr,
^
I googled for the error for several hours but couldn't find anything related to this problem. Does anybody know what is the issue and how to fix it?
The code for UDP client is below
// Client side implementation of UDP client-server model
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netdb.h>
#define PORT 8080
#define MAXLINE 1024
// Driver code
int main() {
int sockfd;
char buffer[MAXLINE];
char *hello = "Hello from client";
struct sockaddr_in servaddr;
// Creating socket file descriptor
if ( (sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0 ) {
perror("socket creation failed");
exit(EXIT_FAILURE);
}
memset(&servaddr, 0, sizeof(servaddr));
// Filling server information
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(PORT);
servaddr.sin_addr.s_addr = INADDR_ANY;
int n, len;
sendto(sockfd, (const char *)hello, strlen(hello),
MSG_CONFIRM, (const struct sockaddr *) &servaddr,
sizeof(servaddr));
printf("Hello message sent.\n");
while (1)
{
n = recvfrom(sockfd, (char *)buffer, MAXLINE,
MSG_WAITALL, (struct sockaddr *) &servaddr,
&len);
buffer[n] = '\0';
printf("Server : %s\n", buffer);
}
close(sockfd);
return 0;
}

Answer 1

My friend suggest me to define MSG_CONFIRM as 0. He said search what is use for it. You also research it.
#define MSG_CONFIRM 0