关于 error LNK2019 无法解析的外部符号
首先，我在网上找到了很多关于这类型错误的博客什么之类的。我也看了一下，但是问题还未解决。
源代码如下：

C/C++ code

#ifdef _MSC_VER//*// * we do not want the warnings about the old deprecated and unsecure CRT functions// * since these examples can be compiled under *nix as well// */#define _CRT_SECURE_NO_WARNINGS#endif#include "pcap.h"#ifndef WIN32    #include <sys/socket.h>    #include <netinet/in.h>#else    #include <winsock.h>#endif// Function prototypesvoid ifprint(pcap_if_t *d);char *iptos(u_long in);char* ip6tos(struct sockaddr *sockaddr, char *address, int addrlen);int main(){    pcap_if_t *alldevs;    pcap_if_t *d;    char errbuf[PCAP_ERRBUF_SIZE+1];    /* Retrieve the device list */    if(pcap_findalldevs(&alldevs, errbuf) == -1)    {        fprintf(stderr,"Error in pcap_findalldevs: %s\n", errbuf);        exit(1);    }    /* Scan the list printing every entry */    for(d=alldevs;d;d=d->next)    {        ifprint(d);    }    /* Free the device list */    pcap_freealldevs(alldevs);    return 1;}/* Print all the available information on the given interface */void ifprint(pcap_if_t *d){  pcap_addr_t *a;  char ip6str[128];  /* Name */  printf("%s\n",d->name);  /* Description */  if (d->description)    printf("\tDescription: %s\n",d->description);  /* Loopback Address*/  printf("\tLoopback: %s\n",(d->flags & PCAP_IF_LOOPBACK)?"yes":"no");  /* IP addresses */  for(a=d->addresses;a;a=a->next) {    printf("\tAddress Family: #%d\n",a->addr->sa_family);    switch(a->addr->sa_family)    {      case AF_INET:        printf("\tAddress Family Name: AF_INET\n");        if (a->addr)          printf("\tAddress: %s\n",iptos(((struct sockaddr_in *)a->addr)->sin_addr.s_addr));        if (a->netmask)          printf("\tNetmask: %s\n",iptos(((struct sockaddr_in *)a->netmask)->sin_addr.s_addr));        if (a->broadaddr)          printf("\tBroadcast Address: %s\n",iptos(((struct sockaddr_in *)a->broadaddr)->sin_addr.s_addr));        if (a->dstaddr)          printf("\tDestination Address: %s\n",iptos(((struct sockaddr_in *)a->dstaddr)->sin_addr.s_addr));        break;      case AF_INET6:       printf("\tAddress Family Name: AF_INET6\n");#ifndef __MINGW32__ /* Cygnus doesn't have IPv6 */        if (a->addr)          printf("\tAddress: %s\n", ip6tos(a->addr, ip6str, sizeof(ip6str)));#endif        break;      default:        printf("\tAddress Family Name: Unknown\n");        break;    }  }  printf("\n");}/* From tcptraceroute, convert a numeric IP address to a string */#define IPTOSBUFFERS    12char *iptos(u_long in){    static char output[IPTOSBUFFERS][3*4+3+1];    static short which;    u_char *p;    p = (u_char *)∈    which = (which + 1 == IPTOSBUFFERS ? 0 : which + 1);    sprintf(output[which], "%d.%d.%d.%d", p[0], p[1], p[2], p[3]);    return output[which];}#ifndef __MINGW32__ /* Cygnus doesn't have IPv6 */char* ip6tos(struct sockaddr *sockaddr, char *address, int addrlen){    socklen_t sockaddrlen;    #ifdef WIN32    sockaddrlen = sizeof(struct sockaddr_in6);    #else    sockaddrlen = sizeof(struct sockaddr_storage);    #endif    if(getnameinfo(sockaddr,        sockaddrlen,        address,        addrlen,        NULL,        0,        NI_NUMERICHOST) != 0) address = NULL;    return address;}#endif /* __MINGW32__ */

我用VS2010调试出现的问题下：
错误1error LNK2019: 无法解析的外部符号 _pcap_freealldevs，该符号在函数 _main 中被引用
错误2error LNK2019: 无法解析的外部符号 _pcap_findalldevs，该符号在函数 _main 中被引用
错误3error LNK2019: 无法解析的外部符号 __imp__getnameinfo@28，该符号在函数 "char * __cdecl ip6tos(struct sockaddr *,char *,int)" (?ip6tos@@YAPADPAUsockaddr@@PADH@Z) 中被引用

错误4error LNK1120: 3 个无法解析的外部命令


说明，此程序要安装Wincap4_1_2 以及相关sdk开发包。


谢谢各位大神了！

[解决办法]
1.可能是对应的库没有包含到工程中.
2.库版本不对,没有_pcap_freealldevs或者参数不匹配.所以link是查不到.
[解决办法]
你没包含相应版本的lib文件