3-3 単純なUDP受信プログラム

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

int
main()
{
  int sock;
  struct sockaddr_in addr;
  struct sockaddr_in senderinfo;
  socklen_t addrlen;
  char buf[2048];
  int n;

  /* (1) */
  sock = socket(AF_INET, SOCK_DGRAM, 0);

  /* (2) */
  addr.sin_family = AF_INET;
  addr.sin_port = htons(12345);
  addr.sin_addr.s_addr = INADDR_ANY;
  bind(sock, (struct sockaddr *)&addr, sizeof(addr));

  /* (3) */
  addrlen = sizeof(senderinfo);
  n = recvfrom(sock, buf, sizeof(buf) - 1, 0,
          (struct sockaddr *)&senderinfo, &addrlen);

  write(fileno(stdout), buf, n);

  /* (4) */
  close(sock);

  return 0;
}

拙著「Linuxネットワークプログラミング」の紹介