Create Simple Port Scanning Program Using C language

Namaste Friends,




Today, In This Post I am going to share with you, a very simple port scanning program created in C language. To Run This Program, You Just Need Linux and GCC.

This Program is very easy to use and fast. But Please Keep In Mind, This Is only for Educational And Practise Purpose Only.

Basically, Guys To make this program more easy to understand, I had used lots of comments. so,
I am hoping that you all guys will manage to understand the basic concept behind this program.

Hmm, Let's me tell you a bit about the concept behind this program, as we know To make a two side connection, We required two entities. first client and second sever. so, here our basic agenda is to find, open port on the server. So, in simple words, our program will act like a client and will bruteforcelly try to connect to all given port. if the connection gets complete.. means the port is open, otherwise port is close.


Note:

1. These Scripts are Tested In Ubuntu Only.
2. For More Description About Syntax, Use Ubuntu man page.


Port Scanner In C.



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/*
 * 
 *      __author__: Suraj Singh Bisht
 *                  surajsinghbisht054@gmail.com
 *                  www.bitforestinfo.com 
 * 
 * ============================================================
 *                 Created During C socket practise
 * ============================================================
 * 
 *  Tested On :
 *          Linux parrot 4.14.0-parrot13-amd64 #1 SMP Parrot 4.14.13-1parrot13 (2018-01-21) x86_64 GNU/Linux
 *          gcc (Debian 7.3.0-5) 7.3.0
 *
 * */

// include header
#include <stdlib.h>     // standard library
#include <stdio.h>      // Standard Input Output Library
#include <sys/socket.h> // socket header
#include <sys/types.h>  // Data types
#include <string.h>     // String
#include <netinet/in.h>
#include <arpa/inet.h> //
#include <unistd.h>

#define PORT_EXPRESSION_ITER 11


// Error Report On Screen
void error(char *msg)
{
    printf("[Error] %s\n", msg);
    printf("[X] Terminating Program...\n");
    exit(0);
}

// Data Type
typedef struct list{
    int data;
    int status;
    struct list * next;
} plist;

// append nodes
void listappend(plist *head, int val){
    /*
    *
    *  To Append New Node Into Linked List Structure.
    */

    plist *tmp;
    
    // starting point
    if(head->next == NULL){
        tmp = malloc(sizeof(plist));
        if (tmp==NULL){
            error("Error During Allocating Node For Port Storing List");
        }
        tmp->data = val;
        tmp->next = NULL;
        tmp->status = 0;
        head->next = tmp;
    }
    else{
        while(head->next!=NULL){
            //printf("Checking Node %i\n", head->data);
            tmp = head->next;
            head = tmp;


            //exit(0);
        }
        tmp = malloc(sizeof(plist));
        tmp->data = val;
        tmp->next = NULL;
        tmp->status = 0;
        head->next = tmp;    
    }
}

void expandlist(plist *head){
    /*
    *
    * This Function is dedicated To explore all node data value Into Terminal.
    * 
    */
    plist *tmp;
    while(head->next!=NULL){
            printf("Node->Data %i\n", head->data);
            tmp = head->next;
            head = tmp;


            //exit(0);
        }
        printf("Node->Data %i\n", head->data);

}
void checkport(int sockd, struct sockaddr_in client, int port, char *ip, plist *node){
    
    client.sin_port = htons(port);
    client.sin_addr.s_addr = inet_addr(ip);
    if(connect(sockd, (struct sockaddr*)&client, sizeof (client))<0){
        node->status=0;
        printf("Close\n");
    }else{
        node->status=2;
        printf("Open\n");
    }

    
}


void portscanner(plist *p, char *ip){
    /*
    * This Function is Completely Dedicated To Perform Port scanning
    * process and save result into linked list status block
    * 
    */
    int sockd;
    plist *tmp;
    tmp = p->next;
    p = tmp;
    
    /*
    
    struct sockaddr_in {
        short   sin_family;
        u_short sin_port;
        struct  in_addr sin_addr;
        char    sin_zero[8];
    };
    
    */
   struct sockaddr_in victim;

   sockd = socket(AF_INET, SOCK_STREAM, 0);
   
    struct timeval timeout;
    timeout.tv_sec  = 1;  // after 1 seconds connect() will timeout
    timeout.tv_usec = 0;

    setsockopt(sockd, SOL_SOCKET, SO_SNDTIMEO, &timeout, sizeof(timeout));

   if (sockd<0){
       error("[Error] During Creation Of Socket Handler");
   }
   victim.sin_family = AF_INET;
   while (p->next!=NULL){
        printf("Scanning IP :%s | Port : %i ---> ", ip, p->data);
        checkport(sockd, victim, p->data, ip, p);
        tmp = p->next;
        p = tmp;

   }
        printf("Scanning IP :%s | Port : %i ---> ", ip, p->data);
        checkport(sockd, victim, p->data, ip, p);
        tmp = p->next;
        p = tmp;

   close(sockd);

}



void ranger(char *exp, plist *p){
    /*
    *
    * This Function is completely Dedicated To Generate Port Integers From Provided
    * Port Expression.
    * 
    */

    char s[6], e[6], *n; 
    int sn, en, i;

    // Get Tail
    n = strpbrk(exp, "-");

    // Store it In another variable
    // surpass '-' char
    n++;

    // copy value in ending variable
    strcpy(e, n);
    
    // convert string into integers
    en = atoi(e);

    // get head
    n = strtok(exp, "-");

    // store in another variable
    strcpy(s, n);
    
    // convert string into integers
    sn = atoi(s);
    
    // check range
    if (sn >= en)
    {
    //printf("Starting From : %s, End at : %s\n",s,e);
               //printf("Starting From : %i, End at : %i\n",sn,en);
;        error("Incorrect Range Found");
    }
    
    for (i = sn; i < en; i++)
    {
        listappend(p, i);
    }
}



// Argument Parser And Processing Function
void argument_parse(char *ip, char *port){
    /*
    *
    * This Function Is Completely Dedicated To Extract Port Integers From Port Expressions
    * And Also Generate Port Integers From Provided Port Range Expression.
    * 
    */

    plist *p;    // Port List Object Define

    p = malloc(sizeof(plist)); // Allocate Space For List Object
    p->next = NULL;
    p->data = 0;
    p->status = -1;

    int l = strlen(port); // length of characters in port expression
    char c;                // to handle every single character of port expression
    char pnum[PORT_EXPRESSION_ITER];
    int pn = 0, iport;

    bzero(pnum, sizeof(pnum)); // make sure, space is clear


    // iter all characters of port expresion
    for (int i = 0; i < l; i++)
    {
        c = port[i];

        // check if character is a valid expression
        if ((c == ' ') |
            (c == '1') |
            (c == '2') |
            (c == '3') |
            (c == '4') |
            (c == '5') |
            (c == '6') |
            (c == '7') |
            (c == '8') |
            (c == '9') |
            (c == '0') |
            (c == '-') |
            (c == ','))
        {
            // Start Storing Characters
            if (pn == 0)
            {
                bzero(pnum, sizeof(pnum));
                pnum[pn] = c;   // string starting
                pnum[PORT_EXPRESSION_ITER] = '\0'; // string end
                pn++;
            }

            // Split Expression And Save Into List 
            else if ((c == ',') & (pn != 0))
            {
                // check if range expression
                if (strpbrk(pnum, "-"))
                {
                    ranger(pnum, p);
                }
                else
                {
                    iport = atoi(pnum);
                    listappend(p ,iport);
                }

                // Reset Input character collector
                pn = 0;
                bzero(pnum, sizeof(pnum));
            }
           

            else if ((pn == 5)&(!strpbrk(pnum, "-")))
            {
                
                // check if range expression
                if (strpbrk(pnum, "-"))
                {
                    ranger(pnum, p);
                }
                else
                {
                    
                    iport = atoi(pnum);
                    listappend(p ,iport);
                }

                // Reset Input character collector
                pn = 0;
                bzero(pnum, sizeof(pnum));
                pnum[pn] = c;   // string starting
                pnum[PORT_EXPRESSION_ITER] = '\0'; // string end
                pn++;
            }
            else if (pn < 5)
            {
                
                pnum[pn] = c;
                pn++;
            
            }
            else if (strpbrk(pnum, "-"))
            {
                
                pnum[pn] = c;
                pn++;
            
            }
            else
            {

                printf("[-] Port Expression Droped Characters : %i\n", pn);
            }
        }
        else
        {
            //printf("%s", c);
            error("Please Provide Valid Port Range Expressions");
        }
    }

    iport = atoi(pnum);
    listappend(p ,iport);
    //expandlist(p);

    // Reset Input character collector
    pn = 0;
    bzero(pnum, sizeof(pnum));
    portscanner(p, ip);

}

// main function trigger
int main(int argc, char const *argv[]){
    /*
    * This Main Function Is Completely Dedicated To Verify And Filter User
    * Provided Arguments.
    * 
    */

    char ip[16];    // IP Address Expression
    char port[100]; // Port Range expression
    
    // if no arguments passed
    if (argc < 2)
    {
        printf(" Please Provide Arguments To Perform Function\n\n \
    :~$ %s IP_ADDRESS PORT-RANGE\n\nSupported Port Expression 1,2,3-80,5  \n\t\t\t[Note] Range Supported Only In Middle Of Expression \n\t\t\t\t like  port1,(Range: Port2-9) ,port10\n",
               argv[0]);

        error("Program Terminating... \n\t\tCause :- No Input Provided.");
    }

    // If Only One Argument is Provided
    else if (argc < 3)
    {
        printf("Please Provide Arguments To Perform Function\n\n \
    :~$ %s IP_ADDRESS PORT-RANGE\n\n\n",
               argv[0]);

        error("Program Terminating... \n\t\tCause : Insuffecient Input Provided.");
    }

    // Check if Provided Arguments are valid to process
    else if ((argc == 3) & (strlen(argv[1]) < 16) & (strlen(argv[1]) > 8))
    {
        printf("Starting CheckPort Program Design/Written By Surajsinghbisht054@gmail.com\n\n\n");

        strcpy(ip, argv[1]);   // Get IP address
        strcpy(port, argv[2]); // Get Port Range Expression
        argument_parse(ip, port); // Transfer Controls To Argument Parse Function
    }

    // Unformatted Arguments Provided
    else
    {
        printf("Please Provide Correct Arguments To Perform Function\n\n \
    :~$ %s IP_ADDRESS PORT-RANGE\n\n\n",
               argv[0]);

        error("Program Terminating... \n\t\tCause : Unformatted Input Provided.");
    }
    return 0;
}
♥Dcode♥

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