TCP Portscanner

// TCP Portscanner by iotpackets & netflooding

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <errno.h>
#include <netdb.h>

int Timeout;
int least;
int max;

int resolve(char *  , char *);
int resolve(char * site , char* ip)
{
    struct hostent *he;
    struct in_addr **addr_list;
    int i;

    if ( (he = gethostbyname( site ) ) == NULL)
    {
        // get the host info
        herror("gethostbyname");
        return 1;
    }

    addr_list = (struct in_addr **) he->h_addr_list;

    for(i = 0; addr_list[i] != NULL; i++)
    {
        //Return the first one;
        strcpy(ip , inet_ntoa(*addr_list[i]) );
        return 0;
    }

    return 1;
}

void portscan(char *target, int port)
{
    int Socket;
    struct timeval timeout;
    struct sockaddr_in sock;

    if(Timeout < 0 || Timeout == 0)
        Timeout = 3; // set to 3 for default
    timeout.tv_sec = Timeout;
    timeout.tv_usec = 0;
    Socket = socket(AF_INET, SOCK_STREAM, 0);
    setsockopt(Socket, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeout, sizeof(timeout));
    setsockopt(Socket, SOL_SOCKET, SO_SNDTIMEO, (char *)&timeout, sizeof(timeout));
    sock.sin_family = AF_INET;
    sock.sin_port = htons(port);
    sock.sin_addr.s_addr = inet_addr(target);
    if(connect(Socket, (struct sockaddr *)&sock, sizeof(sock)) == -1)
        goto end;
    else
    {
        printf("[\x1b[32m+\x1b[37m] Open Port %s:%d open!\n", target, port);
        goto end;
    }
    end:
    close(Socket);
    return;
}

int main(int argc, char **argv)
{
    if(argc < 5 || argc > 5)
    {
        printf("[\x1b[31m?\x1b[37m] Usage: %s <host> <least> <max> <timeout>\n", argv[0]);
        exit(0);
    }
    char host[60];
    resolve(argv[1], host);
    printf("[\x1b[34m!\x1b[37m] Portscanner started on %s\n", host);
    least = atoi(argv[2]);
    if(least == 0 || least < 0)
        least = 1;
    max = atoi(argv[3]);
    if(max == 0 || max < 0)
        max = 500;
    Timeout = atoi(argv[4]);
    int port;
    for(port=least; port < max; port++)
    {
        portscan(host, port);
    }
    printf("[\x1b[33m?\x1b[37m] Finished, Scanned ports %d - %d\n", least, max);
    return;
}