打洞主要采用的是udp的无面向连接的特性来实现，同过user1连接server，打通user1的对外ip和端口，通过user2连接server，打通uer2对外的ip和端口，然后user1和user2通过彼此已经打通的对外ip和端口实现通讯，下面的测试程序，需要先启动服务器端，然后启动两个客户端，就可以看见效果

    方便他人亦是方便自己，如果觉得还行就点下赞吧，这样可以帮助其他人更快的找到解决问题的方法；有疑问的也可留言哦， 谢谢！

    源代码地址：http://pan.baidu.com/s/1i3Bossd

//Server.cpp

#include <winsock2.h>
 #include <stdio.h>
 #pragma comment(lib, "Ws2_32.lib")
 #define UCHAR_MAX 256int main()
 {
 WSADATA wsaData = {0};
 if (0 != WSAStartup(MAKEWORD(2,2), &wsaData))
 {
 printf ("WSAStartup failed. errno=[%d]\n", WSAGetLastError());
 return -1;
 }SOCKET sockServer = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
 if (SOCKET_ERROR == sockServer)
 {
 printf ("socket server failed. errno=[%d]\n", WSAGetLastError());
 return -2;
 }SOCKADDR_IN addrServer = {0};
 addrServer.sin_family = AF_INET;
 addrServer.sin_addr.s_addr = ADDR_ANY;//inet_addr("192.168.1.2");
 addrServer.sin_port = htons(10000);if (0 != bind(sockServer, (sockaddr*)&addrServer, sizeof(addrServer)))
 {
 printf ("bind server failed.errno=[%d]\n", WSAGetLastError());
 return -3;
 }char pcContent1[UCHAR_MAX] = {0};
 SOCKADDR_IN addrUser1 = {0};int nLen1 = sizeof(addrUser1);
 if (SOCKET_ERROR == recvfrom(sockServer, pcContent1, sizeof(pcContent1), 0, (sockaddr*)&addrUser1, &nLen1))
 {
 printf ("recv user 1 failed.errno=[%d]", WSAGetLastError());
 return -4;
 }
 else 
 {
 printf ("user1 ip=[%s] port=[%d]\n", inet_ntoa(addrUser1.sin_addr), htons(addrUser1.sin_port));
 } char pcContent2[UCHAR_MAX] = {0};
 SOCKADDR_IN addrUser2 = {0};
 int nLen2 = sizeof(addrUser2);
 if (SOCKET_ERROR == recvfrom(sockServer, pcContent2, sizeof(pcContent2), 0, (sockaddr*)&addrUser2, &nLen2))
 {
 printf ("recv user 1 failed.errno=[%d]", WSAGetLastError());
 return -5;
 }
 else 
 {
 printf ("user2 ip=[%s] port=[%d]\n", inet_ntoa(addrUser2.sin_addr), htons(addrUser2.sin_port));
 }if (SOCKET_ERROR == sendto(sockServer, (char*)&addrUser1, nLen1, 0, (sockaddr*)&addrUser2, nLen2))
 {
 printf ("send user 2 data failed.\n", WSAGetLastError());
 return -6;
 }if (SOCKET_ERROR == sendto(sockServer, (char*)&addrUser2, nLen2, 0, (sockaddr*)&addrUser1, nLen1))
 {
 printf ("send user 1 data failed.\n", WSAGetLastError());
 return -6;
 }//Sleep(INFINITE);
 return 0;}

//Client.cpp
 #include <winsock2.h>
 #include <stdio.h>
 #pragma comment(lib, "Ws2_32.lib")
 #define UCHAR_MAX 256
 int main()
 {
 WSADATA wsaData = {0};
 if (0 != WSAStartup(MAKEWORD(2,2), &wsaData))
 {
 printf ("WSAStartup failed. errno=[%d]\n", WSAGetLastError());
 return -1;
 }SOCKET sockClient = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
 if (SOCKET_ERROR == sockClient)
 {
  printf ("socket server failed. errno=[%d]\n", WSAGetLastError());
  return -2;
 }char pcContent1[UCHAR_MAX] = {0};
 SOCKADDR_IN addrServer = {0};
 addrServer.sin_family = AF_INET;
 addrServer.sin_addr.s_addr = inet_addr("10.216.165.104");
 addrServer.sin_port = htons(10000);int nLen1 = sizeof(addrServer);
 if (SOCKET_ERROR == sendto(sockClient, pcContent1, 1, 0, (sockaddr*)&addrServer, nLen1))
 {
  printf ("recv user 1 failed.errno=[%d]", WSAGetLastError());
  return -3;
 }SOCKADDR_IN addrUser = {0};
 char pcContent2[UCHAR_MAX] = {0};
 if (SOCKET_ERROR == recvfrom(sockClient, pcContent2, sizeof(pcContent2), 0, (sockaddr*)&addrServer, &nLen1))
 {
  printf ("recv user 1 failed.errno=[%d]", WSAGetLastError());
  return -5;
 }
 else 
 {
  memcpy (&addrUser, pcContent2, sizeof(addrUser));
  //sprintf (pcContent2, "hello, user ip=[%s] port=[%d]\n", inet_ntoa(addrUser.sin_addr), htons(addrUser.sin_port));
  while(1)
  {
     memset(pcContent2,0,UCHAR_MAX);
     printf("请输入您要发送的信息:");
           gets(pcContent2);
   if (SOCKET_ERROR == sendto(sockClient, pcContent2, strlen(pcContent2), 0, (sockaddr*)&addrUser, nLen1))
   {
    printf ("recv user 1 failed.errno=[%d]", WSAGetLastError());
    return -3;
   }
   else 
   {
    if (SOCKET_ERROR == recvfrom(sockClient, pcContent2, sizeof(pcContent2), 0, (sockaddr*)&addrServer, &nLen1))
    {
    printf ("recv user 1 failed.errno=[%d]", WSAGetLastError());
    return -5;
    }
    printf ("%s", pcContent2);
   }
  }
 } Sleep(INFINITE);
 return 0;}