Simple Port Scanner Tool

//Simple Port Scanner - Using C Language
//all libs to run
#include<stdio.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<string.h>
#include<stdlib.h>
#include<unistd.h>
#include<netdb.h>
#include<arpa/inet.h>
#include<pthread.h>
#include<time.h>
//deploy--------------
static char* ip_address;
//---------------------
void mapping_services(int port){
    switch(port){
        case 20: printf("ftp-data"); break;
        case 21: printf("ftp-control"); break;
        case 22: printf("ssh"); break;
        case 23: printf("telnet"); break;
        case 25: printf("smtp"); break;
        case 43: printf("whois"); break;
        case 53: printf("dns"); break;
        case 63: printf("whois++"); break;
        case 69: printf("tftp"); break;
        case 80: printf("http"); break;
        case 107: printf("rtelnet"); break;
        case 109: printf("pop2"); break;
        case 110: printf("pop3"); break;
        case 115: printf("sftp"); break;
        case 118: printf("sql-services"); break;
        case 143: printf("imap"); break;
        case 443: printf("https"); break;
        case 161: printf("snmp"); break;
        case 546: printf("dhcp-client"); break;
        case 547: printf("dhcp-server"); break;
        default: printf("unknow");
    }
}

void* scanning(void* port){
    //---------------------
    int n = *((int*)port);
    pthread_detach(pthread_self());
    int sockfd, check;
    struct sockaddr_in target;
    sockfd = socket(AF_INET, SOCK_STREAM,0);
    bzero((char*)&target, sizeof(target));
    target.sin_family = AF_INET;
    target.sin_addr.s_addr = inet_addr(ip_address);
    target.sin_port = htons(n);
    check = connect(sockfd, (struct sockaddr*)&target, sizeof(target));
    //----------------
    if(check != -1){
        printf("  %d\t open\t   ",n);
        mapping_services(n);
        printf("\n");
    }
    close(sockfd);
    return NULL;
}
//----------------------
int main(int argc, char *argv[]){
    //---------------------
    printf("\n+----------------------------------------------------+\n");
    printf("|THE SIMPLE PORT SCANNER - USING C LANGUAGE - n0Sk!LL|\n");
    printf("+----------------------------------------------------+\n");
    printf("\nUSAGE\n");
    printf("+---------------------------------------------------------------+\n");
    printf("|./scanner <ip-address> (default)                               |\n");
    printf("|./scanner <ip-address> <port-start> <port-end> (set port range)|\n");
    printf("+---------------------------------------------------------------+\n\n");
    if(argc < 2 || argc > 4 || argc == 3){
        perror("Argument is wrong  !!!\n");
        exit(0);
    }

    ip_address = argv[1];
    if(argc == 4){
        int start, end, *port;
        start = atoi(argv[2]);
        end = atoi(argv[3]);
        printf("start: %d  end : %d\n",start,end);
        printf("-PORT-\t-STATE-\t-SERVICE-\n");
        port = &start;
        pthread_t thread_id;
        for(start; start <= end; start++){
            pthread_create(&thread_id, NULL, &scanning,(void*)port);
            sleep(1);
        }
        port = NULL;
    }
    else{
        int i, length, *port;
        pthread_t thread_id;
        int port_list[]={20,21,22,23,25,43,53,63,69,80,107,109,110,115,118,143,161,443,546,547};
        port = port_list;
        length = sizeof(port_list) / sizeof(int);
        printf("-PORT-\t-STATE-\t-SERVICE-\n");
        for(i = 0; i < length; i++){
            pthread_create(&thread_id, NULL, &scanning,(void*)(port+i));
            sleep(1);
        }
        port = NULL;
    }
//-------------------
    return 0;
}

//author:dienpv.uet
//this program run on linux/unix not windows
//to run, you can type command(linux): gcc -o scanner.c outfile -pthread (beacause using multi-thread)