Programming

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define BUFFSIZE 150
int main(){
  struct sockaddr_in serv;
  char buff[BUFFSIZE];
  int sockfd,n;
  if((sockfd=socket(PF_INET,SOCK_DGRAM,0))<0)
     err_sys("socket error");
  bzero((char *)&serv,sizeof(serv));
  serv.sin_family=AF_INET;
  serv.sin_addr.s_addr=inet_addr("10.10.10.9");
  serv.sin_port=htons(13);
  if(sendto(sockfd,buff,BUFFSIZE,0,(struct sockaddr *)&serv,sizeof(serv))!=BUFFSIZE)
     err_sys("sendto error");
  if((n=recvfrom(sockfd,buff,BUFFSIZE,0,(struct sockaddr *)NULL,(int *)NULL))<2)
     err_sys("recvfrom error");
  buff[n-2]=0;
  printf("%s\n",buff);
}

telnet 10.10.10.9 13