test1.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 <string.h>
#include <errno.h>
#include <arpa/inet.h>

#define BUFFER_SIZE	1024

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 new UDP socket failed: %s\n", strerror(errno));
    exit(1);
  }

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

  struct sockaddr_in server_address;

  memset(&server_address, 0, sizeof(server_address));
  server_address.sin_family = PF_INET;
  server_address.sin_port = htons(atoi(argv[2]));
  server_address.sin_addr.s_addr = inet_addr(argv[1]);

  //int bind(int sockfd, struct sockaddr *my_addr, socklen_t addrlen);
  if (bind(fd, (struct sockaddr *) &server_address, sizeof(server_address)) < 0)
  {
    fprintf(stderr, "Bind failed: %s\n", strerror(errno));
    close(fd);
    exit(1);
  }

#ifdef _DEBUG_
  fprintf(stdout, "Bound on %s:%d\n", argv[1], atoi(argv[2]));
#endif

  char buf[BUFFER_SIZE];
  struct sockaddr_in peer_address;
  socklen_t peer_address_length;
  ssize_t n;

  peer_address_length = sizeof(peer_address);

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

    //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, "Read %d bytes from %s:%d\n", n, inet_ntoa(peer_address.sin_addr), ntohs(peer_address.sin_port));
#endif

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

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

#ifdef _DEBUG_
    fprintf(stdout, "Write %d bytes to %s:%d\n", n, inet_ntoa(peer_address.sin_addr), ntohs(peer_address.sin_port));
#endif
  }

  close(fd);

  return 0;
}