#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <pthread.h>
#define CHECK_ERROR(p, m) \
do { \
if (p) { \
fprintf(stderr, "ERROR " m "\n"); \
exit(1); \
} \
} while (0)
const int kBufSize = 10;
int sockfd;
static void *client_thread_udp(void *data) {
#ifdef SENDTO
const char buf[kBufSize / 2] = {0, };
#else
const char buf[kBufSize] = {0, };
#endif
struct sockaddr_in serveraddr;
socklen_t addrlen = sizeof(serveraddr);
int succeeded = getsockname(sockfd, (struct sockaddr *)&serveraddr, &addrlen);
CHECK_ERROR(succeeded < 0, "in getsockname");
succeeded = sendto(sockfd, buf, kBufSize, 0, (struct sockaddr *)&serveraddr,
sizeof(serveraddr));
CHECK_ERROR(succeeded < 0, "in sending message");
return NULL;
}
int main() {
#ifdef RECVFROM
char buf[kBufSize / 2];
#else
char buf[kBufSize];
#endif
pthread_t client_thread;
struct sockaddr_in serveraddr;
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
CHECK_ERROR(sockfd < 0, "opening socket");
memset(&serveraddr, 0, sizeof(serveraddr));
serveraddr.sin_family = AF_INET;
serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);
serveraddr.sin_port = 0;
int bound = bind(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr));
CHECK_ERROR(bound < 0, "on binding");
int succeeded =
pthread_create(&client_thread, NULL, client_thread_udp, &serveraddr);
CHECK_ERROR(succeeded, "creating thread");
recvfrom(sockfd, buf, kBufSize, 0, NULL, NULL);
succeeded = pthread_join(client_thread, NULL);
CHECK_ERROR(succeeded, "joining thread");
return 0;
}