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#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#define BUFSZ 256
#define SERVICE "daytime"
main(argc, argv)
int argc;
char **argv;
{
int s, n, len;
char buf[BUFSZ];
struct hostent *hp;
struct servent *sp;
struct sockaddr_in sin;
/*
* Get a datagram socket in the Internet
* domain.
*/
if ((s = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
perror("socket");
exit(1);
}
/*
* Look up the port number of the service.
*/
if ((sp = getservbyname(SERVICE, "udp")) == NULL) {
fprintf(stderr, "%s/udp: unknown service.\n", SERVICE);
exit(1);
}
/*
* For each host on the command line...
*/
while (--argc) {
/*
* Look up the network number of
* the host.
*/
if ((hp = gethostbyname(*++argv)) == NULL) {
fprintf(stderr, "%s: host unknown.\n", *argv);
continue;
}
/*
* Build the address of the server on
* the remote machine.
*/
sin.sin_family = AF_INET;
sin.sin_port = sp->s_port;
bcopy(hp->h_addr, &sin.sin_addr, hp->h_length);
/*
* Print the name of the host.
*/
printf("%s: ", *argv);
fflush(stdout);
/*
* Send a datagram to the server.
*/
if (sendto(s, buf, BUFSZ, 0, &sin, sizeof(sin)) < 0) {
perror("sendto");
continue;
}
/*
* Receive a datagram back.
*/
len = sizeof(sin);
n = recvfrom(s, buf, sizeof(buf), 0, &sin, &len);
if (n < 0) {
perror("recvfrom");
continue;
}
/*
* Print the datagram.
*/
buf[n] = NULL;
printf("%s\n", buf);
}
close(s);
exit(0);
}
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