#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/select.h>
#include <errno.h>
#include <inttypes.h>

void error(char *msg)
{
  perror(msg);
  exit(1);
}

char* scan(int begin, int end, char* ip, int timeout)
{
    int socketfd, retval;
    fd_set rfds;

    //set timeout
    struct timeval tv;
    tv.tv_sec = 0;

    //create address
    struct sockaddr_in address;

    //zero address memory
    memset(&address,0, sizeof(address));

    //initialize address
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = inet_addr(ip);
    if (address.sin_addr.s_addr == -1)
        error("Invalid IP address format");

    int port;
    for (port = begin; port <= end; ++port)
    {
        //set port in network bit order
        address.sin_port = htons(port);

        //get socket file descriptor
        socketfd = socket(AF_INET, SOCK_STREAM, 0);
        if (socketfd < 0)
            error("ERROR opening socket");

        //add socket descriptor to set
        FD_ZERO(&rfds);
        FD_SET(socketfd, &rfds);

        //make socket non-blocking
        int flags = fcntl(socketfd, F_GETFL, 0);
        fcntl(socketfd, F_SETFL, flags | O_NONBLOCK);

        //try to connect
        retval = connect(socketfd,(struct sockaddr *)&address,sizeof(address));

        //on failure to connect
        if (retval == -1)
        {
            //if connection is waiting
            if (errno == EINPROGRESS)
            {
                //reset timeout value
                tv.tv_usec = timeout;

                //wait until descriptor in set becomes writable, or operation times out
                retval = select(socketfd+1,NULL,&rfds,NULL,&tv);
                if (retval == -1)
                {
                    error("select() failed");
                }
                else if (retval)
                {
                    //check if something went wrong
                    int optval, len;
                    getsockopt(socketfd,SOL_SOCKET,SO_ERROR,&optval,&len);

                    //print appropriate message
                    if (optval)
                    {
                        if (optval == ECONNREFUSED)
                            printf("%d::closed\n",port);
                        else
                        {
                            printf("Error value:%d %d::error\n",optval,port);
                        }
                    }
                    else
                        printf("%d::open\n",port);
              }
              else
              {
                  printf("%d::timed out\n",port);
              }
            }
        }
        close(socketfd);
    }
    return NULL;
}

int main(int argc, char* argv[])
{
    int begin, end, timeout;
    char ip[16];

    int i;
    for (i = 0; i < argc; ++i)
    {
        //if argument starts with '-'
        if (argv[i][0] == '-')
        {
            switch (argv[i][1])
            {
                case 'a':
                {
                    strncpy(ip,argv[++i],15);
                    break;
                }
                case 'b':
                {
                    begin = atoi(argv[++i]);
                    break;
                }
                case 'e':
                {
                    end = atoi(argv[++i]);
                    break;
                }
                case 't':
                {
                    timeout = atoi(argv[++i]);
                    break;
                }
                default:
                {
                    error("Invalid argument");
                }
            };
        }
    }

    //printf("begin: %d\nend: %d\naddress: %s\ntimeout: %d\n",begin,end,ip,timeout);

    char* result = scan(begin,end,ip,timeout);
    return 0;
}