udpclient.c

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>

static void help(void)
{
  printf("UDP client for test purpose\n");
  printf("client <ip_to_use> <port_to_use>\n");
}


int main(int argc, char * argv[])
{
  int sock;
  struct sockaddr_in server_addr;
  struct hostent * host = NULL;
  char * send_data = NULL;
  size_t size = 0;
  ssize_t len = 0;

  if (argc < 3) {
    help();
    exit(1);
  }

  host= (struct hostent *) gethostbyname((char *)argv[1]);

  if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
    perror("socket");
    exit(1);
  }

  server_addr.sin_family = AF_INET;
  server_addr.sin_port = htons(atoi(argv[2]));
  server_addr.sin_addr = *((struct in_addr *)host->h_addr);
  bzero(&(server_addr.sin_zero),8);

  printf("Sending to %s:%d\n", inet_ntoa(server_addr.sin_addr), ntohs(server_addr.sin_port));

  while (1) {
    printf("Type Something (q or Q to quit):");
    if ((len = getline(&send_data, &size, stdin)) > 0) {
      len--;
      send_data[len] = '\0';
      if (strncasecmp(send_data , "q", len) == 0) {
        break;
      } else {
        fprintf(stdout, "sending %s size %u", send_data, (unsigned int)len);
        sendto(sock, send_data, len, 0,
               (struct sockaddr *)&server_addr, sizeof(struct sockaddr));
      }
      free(send_data);
      send_data = NULL;
      size = 0;
      len = 0;
    } else {
      break;
    }
  }
  return 0;
}