关于winpcap的问题

[k3ner1]

我已经将网卡设置位混杂模式了，但是在代码中加入

if(-1 == pcap_compile(pd,&filter,filter_app,1,0))
    {
          fprintf(stderr,"编译过滤器失败！");
          exit(2); 
    }
    
    pcap_setfilter(pd,&filter);[

好像就开始只嗅探本机的相应代码了。当把上面的代码去掉的时候就可以接收网内的数据包了，这是为什么啊？
完整代码如下：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pcap.h>
void sniffer_pcap();
void print_if_info(pcap_if_t *rs);
void print_packet_context(u_char *user,const struct pcap_pkthdr *h,const u_char *p);
int main(int argc,char*argv[])
{
    sniffer_pcap();
    system("PAUSE");
    return 0;
}
void sniffer_pcap()
{
    pcap_if_t *alldevs;
    pcap_if_t *cur,*p;
    struct bpf_program filter;
    struct pcap_pkthdr *header;
    char filter_app[] = "port 23";
    const u_char *packet;
    u_int i;
    char errbuf[PCAP_ERRBUF_SIZE+1];
    if(-1 == pcap_findalldevs(&alldevs,errbuf))
    {
        fprintf(stderr,"find devs faild!");
        exit(1);
    }
    else
    {
        cur = alldevs;
        while(cur != NULL)
        {
            print_if_info(cur);
            p = cur;
            cur = cur->next;
        }
    }
    pcap_t *pd = pcap_open_live(p->name,65535,1,1000,errbuf);
 /*   if(-1 == pcap_compile(pd,&filter,filter_app,1,0))
    {
          fprintf(stderr,"编译过滤器失败！");
          exit(2); 
    }
    
    pcap_setfilter(pd,&filter);*/
    while(1)
    {
      pcap_next_ex(pd,&header,&packet);
   // pcap_loop(pd,20,print_packet_context,NULL);
      printf("packet length is:[%ld]\n",header->len);
      printf("packet context:[");
    for(i = 1;(i<(header->caplen+1));i++)
    {
            printf("%c",packet[i-1]);
    
    }
    printf("]\n");
}
    pcap_freealldevs(alldevs);
    pcap_close(pd);
    free(cur);
    free(p);
}
void print_if_info(pcap_if_t *rs)
{
     printf("dev name:%s\n",rs->name);
     printf("dev description:%s\n",rs->description);
}
void print_packet_context(u_char *user,const struct pcap_pkthdr *h,const u_char *p)
{
     int i;
     printf("packet length:[%d]\n",h->len);
     printf("get packet length:[%d]\n",h->caplen);
    printf("packet context:[");
    for(i = 1;(i<(h->caplen+1));i++)
    {
            printf("%c",p[i-1]);
    
    }
}

[k3ner1]

我是新人没那么多分数给，见谅~~~