A Simple Port Scanner Written In C

#include<stdio.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<stdlib.h>
#include<netdb.h>
int main(int argc,char **argv)
{
        int i,err,net;
        struct hostent *host;
        struct sockaddr_in sa;
        if(argc!=2){
                printf("Error...Usage :%s ip-address",argv[0]);
                exit(0);
        }
        for(i=1;i<20000;i++){
                sa.sin_family=AF_INET;
                sa.sin_port=htons(i);
                sa.sin_addr.s_addr=inet_addr(argv[1]);
                net=socket(AF_INET,SOCK_STREAM,0);
            err=connect(net,(struct sockaddr_in *)&sa,sizeof(sa));
        if(err>=0){
                        printf("\n%d is open",i);
                }
                close(net);
        }
        printf("\n");
}