取得拨号上网时动态分配IP的两种方法
1:使用socket函数。
在拨号前先取得所有本地IP，记录到字符串列表里。
拨号成功后再遍历一次所有本地IP,和已经记录在字符串列表里IP比较。新增加的IP地址就是拨号上网时动态分配IP了。
2:使用和RAS有关API。
在vc里可以方便使用和ras相关的API。但在C++Builder 6里会出现由版本不同引起的错误。
所以在BCB里关键是要自己指定函数的大小。
以下代码在win2000 + C++Builder 6 环境下编译通过。
在Form里添加2个Edit,3个Button;
//---------------------------------------------------------------------------
#ifndef Unit1H
#define Unit1H
//---------------------------------------------------------------------------
#include <Classes.hpp>
#include <Controls.hpp>
#include <StdCtrls.hpp>
#include <Forms.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published: // IDE-managed Components
TEdit *Edit1;
TButton *Button1;
TButton *Button2;
TEdit *Edit2;
TButton *Button3;
void __fastcall Button1Click(TObject *Sender);
void __fastcall Button2Click(TObject *Sender);
void __fastcall Button3Click(TObject *Sender);
private: // User declarations
TStringList *m_slIp;
public: // User declarations
__fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif
//---------------------------------------------------------------------------
#include <vcl.h>
#pragma hdrstop
#include "Unit1.h"
#include <winsock2.h>
#include <ras.h>
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
: TForm(Owner)
{
m_slIp = new TStringList();
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
WORD wVersionRequested;
WSADATA wsaData;
char cHostName[64] = {0};
HOSTENT *pHost = NULL;
AnsiString psIp;
int Index;
wVersionRequested = MAKEWORD(2, 0);
if(0 != WSAStartup(wVersionRequested, &wsaData))
{
WSACleanup();
ShowMessage("socket版本号不对");
}
if(0 == gethostname(cHostName, 64))
{
pHost = gethostbyname(cHostName);
if(pHost != NULL)
{
for(int i=0; pHost->h_addr_list[i]!=NULL; i++)
{
IN_ADDR *p = (IN_ADDR *)(pHost->h_addr_list[i]);
psIp = inet_ntoa(*p);
m_slIp->Add(psIp); //IP地址存入字符串列表
}
}
else
{
WSACleanup();
ShowMessage("取IP地址失败");
}
}
else
{
ShowMessage("取机器名失败");
}
WSACleanup();
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button2Click(TObject *Sender)
{
RASCONN RASconn; //活动连接
DWORD BuffSize ; //活动连接所占内存大小；
DWORD ConnNum; //活动连接数目
RASconn.dwSize=692; //必须指定一个连接的内存大小；
BuffSize=692;
RASPPPIP rip;
AnsiString ModemIp;
ZeroMemory(&rip, sizeof(rip));
DWORD size;
size = 40;
rip.dwSize = 40;
DWORD dwReturn=RasEnumConnections(&RASconn,&BuffSize,&ConnNum);
if(dwReturn==0)
{
if(ConnNum>0)
{
//ShowMessage("没有拨号连接！");
if ( (RasGetProjectionInfo(RASconn.hrasconn,RASP_PppIp,
&rip, &size ) ) != 0 )
{
ShowMessage("取IP地址失败");
}
else
{
Edit2->Text = rip.szIpAddress ;
}
}
else
{
ShowMessage("没有拨号连接！");
}
}
else
ShowMessage("RasEnumConnections函数失败！");
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button3Click(TObject *Sender)
{
WORD wVersionRequested;
WSADATA wsaData;
char cHostName[64] = {0};
HOSTENT *pHost = NULL;
AnsiString psIp;
int Index;
wVersionRequested = MAKEWORD(2, 0);
if(0 != WSAStartup(wVersionRequested, &wsaData))
{
WSACleanup();
ShowMessage("socket版本号不对");
}
if(0 == gethostname(cHostName, 64))
{
pHost = gethostbyname(cHostName);
if(pHost != NULL)
{
for(int i=0; pHost->h_addr_list[i]!=NULL; i++)
{
IN_ADDR *p = (IN_ADDR *)(pHost->h_addr_list[i]);
psIp = inet_ntoa(*p);
if(m_slIp->IndexOf(psIp) < 0)
{
Edit1->Text = psIp;
}
}
}
else
{
WSACleanup();
ShowMessage("取IP地址失败");
}
}
else
{
ShowMessage("取机器名失败");
}
WSACleanup();
delete m_slIp;
}
//---------------------------------------------------------------------------
先在上网前单击Button1，
上网后再单击Butto3得到就是拨号IP. 
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