test2.c

学习linux的软件

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>
#include <errno.h>

#define BUFFER_SIZE	1024

char *banner = "Hello world!";

int main(int argc, char **argv)
{
  int fd;

  if (argc < 3)
  {
    fprintf(stdout, "Usage: %s <ip> <port>\n", argv[0]);
    return 0;
  }

  if ((fd = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
  {
    fprintf(stderr, "Create UDP socket failed: %s\n", strerror(errno));
    exit(1);
  }

#ifdef _DEBUG_
  fprintf(stdout, "Created a new UDP socket %d\n", fd);
#endif

  char buf[BUFFER_SIZE];

  memset(buf, 0, sizeof(buf));

  struct sockaddr_in remote_address;
  struct sockaddr_in peer_address;
  socklen_t peer_address_length;

  int n;

  memset(&remote_address, 0, sizeof(remote_address));

  remote_address.sin_family = PF_INET;
  remote_address.sin_addr.s_addr = inet_addr(argv[1]);
  remote_address.sin_port = htons(atoi(argv[2]));

  //memcpy(buf, banner, strlen(banner));

  //char *fgets(char *s, int size, FILE *stream);
  fgets(buf, sizeof(buf), stdin);

  //ssize_t sendto(int s, const void *buf, size_t len, int flags, const struct sockaddr *to, socklen_t tolen);
  n = sendto(fd, buf, strlen(buf), 0, (struct sockaddr *) &remote_address, sizeof(remote_address));

#ifdef _DEBUG_
  fprintf(stdout, "Sent %d bytes to remote host %s:%d\n", n, argv[1], atoi(argv[2]));
#endif

  memset(buf, 0, sizeof(buf));
  peer_address_length = sizeof(peer_address);

  //ssize_t recvfrom(int s, void *buf, size_t len, int flags, struct sockaddr *from, socklen_t *fromlen);
  n = recvfrom(fd, buf, sizeof(buf), 0, (struct sockaddr *) &peer_address, &peer_address_length);

#ifdef _DEBUG_
  fprintf(stdout, "Received %d from remote host %s:%d\n", n, inet_ntoa(peer_address.sin_addr), ntohs(peer_address.sin_port));
#endif

  fprintf(stdout, "Message from remote: %s\n", buf);

  close(fd);

  return 0;
}