3-16 bind()を使った名前確認

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
void
print_my_port_num(int sock)
{
struct sockaddr_in s;
socklen_t sz = sizeof(s);
getsockname(sock, (struct sockaddr *)&s, &sz);
printf("%d\n", ntohs(s.sin_port));
}
int
main()
{
int sock;
struct sockaddr_in addr;
struct sockaddr_in myname;
int n;
sock = socket(AF_INET, SOCK_DGRAM, 0);
print_my_port_num(sock);
addr.sin_family = AF_INET;
addr.sin_port = htons(12345);
inet_pton(AF_INET, "127.0.0.1", &addr.sin_addr.s_addr);
myname.sin_family = AF_INET;
myname.sin_addr.s_addr = INADDR_ANY;
myname.sin_port = htons(54321);
bind(sock, (struct sockaddr *)&myname, sizeof(myname));
print_my_port_num(sock);
n = sendto(sock, "HELLO", 5, 0, (struct sockaddr *)&addr, sizeof(addr));
if (n < 1) {
perror("sendto");
return 1;
}
print_my_port_num(sock);
close(sock);
return 0;
}

拙著「Linuxネットワークプログラミング」の紹介