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pktdump_ex example
[Using WinPcap in your programs]

/*
 * Copyright (c) 1999 - 2002
 *  Politecnico di Torino.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that: (1) source code distributions
 * retain the above copyright notice and this paragraph in its entirety, (2)
 * distributions including binary code include the above copyright notice and
 * this paragraph in its entirety in the documentation or other materials
 * provided with the distribution, and (3) all advertising materials mentioning
 * features or use of this software display the following acknowledgement:
 * ``This product includes software developed by the Politecnico
 * di Torino, and its contributors.'' Neither the name of
 * the University nor the names of its contributors may be used to endorse
 * or promote products derived from this software without specific prior
 * written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#include <stdlib.h>
#include <stdio.h>

#include <pcap.h>

#define LINE_LEN 16

main(int argc, char **argv) {
    
    pcap_if_t *alldevs, *d;
    pcap_t *fp;
    u_int inum, i=0;
    char errbuf[PCAP_ERRBUF_SIZE];
    int res;
    struct pcap_pkthdr *header;
    u_char *pkt_data;

    printf("pktdump_ex: prints the packets of the network using WinPcap.\n");
    printf("\t Usage: pktdump_ex [-n adapter] | [-f file_name]\n\n");

    if(argc < 3){

        /* The user didn't provide a packet source: Retrieve the device list */
        if (pcap_findalldevs(&alldevs, errbuf) == -1)
        {
            fprintf(stderr,"Error in pcap_findalldevs: %s\n", errbuf);
            exit(1);
        }
        
        /* Print the list */
        for(d=alldevs; d; d=d->next)
        {
            printf("%d. %s", ++i, d->name);
            if (d->description)
                printf(" (%s)\n", d->description);
            else
                printf(" (No description available)\n");
        }
        
        if(i==0)
        {
            printf("\nNo interfaces found! Make sure WinPcap is installed.\n");
            return -1;
        }
        
        printf("Enter the interface number (1-%d):",i);
        scanf("%d", &inum);
        
        if(inum < 1 || inum > i)
        {
            printf("\nInterface number out of range.\n");
            /* Free the device list */
            pcap_freealldevs(alldevs);
            return -1;
        }
        
        /* Jump to the selected adapter */
        for(d=alldevs, i=0; i< inum-1 ;d=d->next, i++);
        
        /* Open the device */
        if ( (fp= pcap_open_live(d->name, 100, 1, 20, errbuf) ) == NULL)
        {
            fprintf(stderr,"\nError opening adapter\n");
            return -1;
        }
    }
    else{
        
        /* The user provided a packet source: open it */
        switch (argv[1] [1])
        {
            
        case 'n':
            {
                /* Open a physical device */
                if ( (fp= pcap_open_live(argv[2], 100, 1, 20, errbuf) ) == NULL)
                {
                    fprintf(stderr,"\nError opening adapter\n");
                    return -1;
                }
            };
            break;
            
        case 'f':
            {
                /* Open a capture file */
                if ( (fp = pcap_open_offline(argv[2], errbuf) ) == NULL)
                {
                    fprintf(stderr,"\nError opening dump file\n");
                    return -1;
                }
            };
            break;
        }
    }

    /* Read the packets */
    while((res = pcap_next_ex( fp, &header, &pkt_data)) >= 0){

        if(res == 0)
            /* Timeout elapsed */
            continue;

        /* print pkt timestamp and pkt len */
        printf("%ld:%ld (%ld)\n", header->ts.tv_sec, header->ts.tv_usec, header->len);          
        
        /* Print the packet */
        for (i=1; (i < header->caplen + 1 ) ; i++)
        {
            printf("%.2x ", pkt_data[i-1]);
            if ( (i % LINE_LEN) == 0) printf("\n");
        }
        
        printf("\n\n");     
    }

    if(res == -1){
        printf("Error reading the packets: %s\n", pcap_geterr(fp));
        return -1;
    }

    return 0;
}

documentation. Copyright (c) 2002-2003 Politecnico di Torino. All rights reserved.