新手写c++，实现截取ip数据包

求教大神，如何实现截取socket中的数据包，并且保存到一个文档中，用c++实现

用winpcap类库来开发

/*
Listing 2. Simple sniffer
To compile: gcc simplesniffer.c -o simplesinffer -lpcap
*/
#pragma comment(lib,"wpcap.lib")
#include
#include

int main(int argc, char **argv)
{
system("clear");
pcap_t *fp;

char errbuf[PCAP_ERRBUF_SIZE];
pcap_t *descr= pcap_open_offline("/home/IPS/test.pcap",errbuf);
const u_char * packet;

struct pcap_pkthdr hdr;

packet = pcap_next(descr, &hdr);
//printf("packet: %s\n",packet);
fflush(stdout);
    /* Open the output device */
    if ( (fp= pcap_open_live("eth3", 100, 1,1000,errbuf ) ) == NULL)
    {
        fprintf(stderr,"\nUnable to open the adapter. %s is not supported \n", "eth3");
        return 0;
    }
        printf("open the output device success!\n");
        getchar();
        while (packet)
        {
            unsigned packetSize= hdr.len;
            printf("packeSize is :%d\n",packetSize);
            unsigned i=0;
            /*              
            for (i=0; i< packetSize;i++)
            {
                //printf("now i is %d\n",i);
                //sleep(2);
            }
            */
            //pcap_sendpacket(sp->handle.pcap, data, (int)len);

            pcap_sendpacket(fp, packet, packetSize);
            packet = pcap_next(descr, &hdr);
            printf("send packet over!:%s \n",descr);
        }
    pcap_close(descr);
    return 0;

}