access data from server udp - c

Question

I have a problem, I have a client server udp, in server side I need to access data from client side to control movement of the robot. For the experiment I use to print "oke" if the value of the data is 1.
here the code program:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#define MYPORT 4950
#define MAXBUFLEN 100
int sockfd;
struct sockaddr_in my_addr;
struct sockaddr_in their_addr;
struct hostent *he;
int addr_len, numbytes;
char dt[30];
char buf[MAXBUFLEN];
int main()
{
printf("‐‐‐‐‐ PROGRAM CHATTING ‐‐‐‐‐\n");
if((sockfd=socket(AF_INET,SOCK_DGRAM,0))==-1){
perror("socket");
exit(1); }
my_addr.sin_family = AF_INET;
my_addr.sin_port = htons(MYPORT);
my_addr.sin_addr.s_addr = INADDR_ANY;
memset(&(my_addr.sin_zero),'\0',8);
if(bind(sockfd,(struct sockaddr *)&my_addr,sizeof(struct sockaddr))==-1){
perror("bind");
exit(1); }
while(1){
addr_len = sizeof(struct sockaddr);
if((numbytes=recvfrom(sockfd,buf,MAXBUFLEN-1,0,(struct sockaddr *)&their_addr,&addr_len))==-1)
{
perror("recvfrom");
exit(1);}
buf[numbytes]='\0';
printf("%s : \"%s\"\n", inet_ntoa(their_addr.sin_addr), buf);
if (buf[0]==1)
{ printf("oke\n");}
printf("Me : ");
scanf("%s", dt);
if((numbytes=sendto(sockfd,dt,strlen(dt),0,(struct sockaddr*)&their_addr,sizeof(struct sockaddr)))==-1)
{
perror("sendto");
exit(1);
}
}
close(sockfd);
return 0;
}
when I put "1" in client side the result is:
‐‐‐‐‐ PROGRAM CHATTING ‐‐‐‐‐
130.130.66.76 : "1"
Me :
even in the program there are:
if (buf[0]==1)
{ printf("oke\n");}
why the program cannot access to inside of if?

Answer 1

Try if (buf[0]=='1')
Number characters map to different ASCII values than their number, so, for example, '1'==49.