#include <stdio.h>#include <stdlib.h>#include <string.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#define PORT 3300#define MSG 1024void udps_respon (int sockfd){ struct sockaddr_in addr; int addrlen; char msg [MSG]; int n; addrlen=sizeof (struct sockaddr); for (;;)    {	n=recvfrom (sockfd, msg, MSG, 0, (struct sockaddr *) &addr, &addrlen);	sendto (sockfd, msg, n, 1, addr, addrlen);    }}int main (){ int sockfd; struct sockaddr_in addr; sockfd=socket (AF_INET, SOCK_DGRAM, 0); if (sockfd<0)    {	fprintf (stderr,"Create socket error\n");	exit (1);    } bzero (&addr,sizeof (addr)); addr.sin_family=AF_INET; addr.sin_addr.s_addr=htonl (INADDR_ANY); addr.sin_port=htons (PORT); if (bind (sockfd, (struct sockaddr * ) &addr, sizeof (addr)) <0)    {	fprintf (stderr,"Error when bind\n");	exit(1);    }  upds_respon (sockfd); close (sockfd);}