Find open ports on given Ip

C - program to find open ports on give IP address.

Program :-


#include<stdio.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>

int main()
{
char ip[20];
struct sockaddr_in addr;
int st_port,end_port,i,skt,use;

printf("\n\tEnter Ip address : ");
gets(ip);

printf("\n\tEnter starting port : ");
scanf("%d",&st_port);

printf("\n\tEnter End port : ");
scanf("%d",&end_port);

for(i=st_port;i<=end_port;i++)
{
skt=socket(PF_INET,SOCK_STREAM,0);
if(skt<0)
{
printf("\n\tERROR : socket() failed ");
exit(0);
}
addr.sin_family=PF_INET;
addr.sin_port=htons(i);
addr.sin_addr.s_addr=inet_addr(ip);
use=connect(skt,(struct sockaddr *)&addr,sizeof(addr));
close(skt);
if(use!=-1)
{
printf("\n\t%d  is running",i);
}
}
}