/* UDP client in the internet domain */
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#define MIN(x, y) ((x) < (y) ? (x) : (y))
#define MAX(x, y) ((x) > (y) ? (x) : (y))
void error(const char *);
int main(int argc, char *argv[])
{
int sock, n;
unsigned int length;
struct sockaddr_in server, from;
struct hostent *hp;
char buffer[256];
if (argc < 3) {
printf("Usage: %s <port>\n", argv[0]);
exit(1);
}
sock= socket(AF_INET, SOCK_DGRAM, 0);
if (sock < 0) error("socket");
server.sin_family = AF_INET;
hp = gethostbyname(argv[1]);
if (hp==0) error("Unknown host");
bcopy((char *)hp->h_addr,
(char *)&server.sin_addr,
hp->h_length);
server.sin_port = htons(atoi(argv[2]));
length=sizeof(struct sockaddr_in);
printf("Please enter the message: ");
bzero(buffer, sizeof(buffer));
fgets(buffer, sizeof(buffer)-1, stdin);
n=sendto(sock,buffer,
strlen(buffer),0,(const struct sockaddr *)&server,length);
if (n < 0)
error("Sendto");
n = recvfrom(sock, buffer, sizeof(buffer), 0, (struct sockaddr *)&from, &length);
if (n < 0)
error("recvfrom");
printf("Got an ack: %d bytes\n", n);
write(1, buffer, MIN(n, strlen(buffer)));
close(sock);
return 0;
}
void error(const char *msg)
{
perror(msg);
exit(0);
}
</pre>
