Portscanner for Linux/Unix in C

A simple portscanner in C.
Works for Linux only .
It detects the open ports for a host.

After compiling using : gcc portscanner.c
Usage : ./a.out <host-IP>

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

int main(int argc, char *argv[])
{
    int sockfd, port;
    struct hostent *he;


    if (argc != 2)
    {
        fprintf(stderr,"usage: client hostname\n");
        exit(1);
    }

    if ((he=gethostbyname(argv[1])) == NULL)    // get the host info
    {
        perror("gethostbyname");
        exit(1);
    }
    for(port=0; port<=65000; port++)
    {
        struct sockaddr_in their_addr; // connector's address information
        if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
        {
            perror("socket");
            exit(1);
        }

        their_addr.sin_family = AF_INET;    // host byte order
        their_addr.sin_port = htons(port);  // short, network byte order
        their_addr.sin_addr = *((struct in_addr *)he->h_addr);
        memset(&(their_addr.sin_zero), '\0', 8);  // zero the rest of the struct

        if (connect(sockfd, (struct sockaddr *)&their_addr, sizeof(struct sockaddr)) == -1)
        {
            close(sockfd);
        }
        else
        {
            printf("%i open\n", port);
            close(sockfd);
        }
    }
}