Lesson17进程间通信

有四种方法

1.剪贴板

 a.创建个ClipBoard的对话框应用程序，加两EditBox和两个Button发送接收。

 b.具体代码：

发送端代码：

if(OpenClipboard())
{
 CString str;
 HANDLE hClip;
 char *pBuf;
 EmptyClipboard();
 GetDlgItemText(IDC_EDIT_SEND,str);
 hClip=GlobalAlloc(GMEM_MOVEABLE,str.GetLength()+1);
 pBuf=(char*)GlobalLock(hClip);将句柄转换为指针！
 strcpy(pBuf,str);
 GlobalUnlock(hClip);
 SetClipboardData(CF_TEXT,hClip);
 CloseClipboard();
}

 接收端代码：

if(OpenClipboard())
{
 if(IsClipboardFormatAvailable(CF_TEXT))
 {
   HANDLE hClip;
   char *pBuf;
   hClip=GetClipboardData(CF_TEXT);
   pBuf=(char*)GlobalLock(hClip);
   GlobalUnlock(hClip);
   SetDlgItemText(IDC_EDIT_RECV,pBuf);
   CloseClipboard();
 }
}

2.匿名管道：只能在父子进程之间进行通信

 a.先建一个Parent的单文档应用程序，增加“创建管道”“读取数据”“写入数据”三个菜单

 b.增加成员变量HANDLE类型的hRead,hWrite，初始化变量，并在析构函数中释放句柄

 c.响应菜单代码：

void CParentView::OnPipeCreate() 菜单“创建管道”代码
{
// TOD Add your command handler code here
SECURITY_ATTRIBUTES sa;
sa.bInheritHandle=TRUE;
sa.lpSecurityDescriptor=NULL;
sa.nLength=sizeof(SECURITY_ATTRIBUTES);
if(!CreatePipe(&hRead,&hWrite,&sa,0))
{
 MessageBox("创建匿名管道失败！");
 return;
}
STARTUPINFO sui;
PROCESS_INFORMATION pi;
ZeroMemory(&sui,sizeof(STARTUPINFO));将数据清0！
sui.cb=sizeof(STARTUPINFO);
sui.dwFlags=STARTF_USESTDHANDLES;
sui.hStdInput=hRead;
sui.hStdOutput=hWrite;
sui.hStdError=GetStdHandle(STD_ERROR_HANDLE);
 
if(!CreateProcess("..\\Child\\Debug\\Child.exe",NULL,NULL,NULL,
   TRUE,0,NULL,NULL,&sui,&pi))创建子进程
{
 CloseHandle(hRead);
 CloseHandle(hWrite);关闭句柄，将内核对象的使用计数减少1，这样当操作系统发现内核对象的使用计数为0时，将清除内核对象。
 hRead=NULL;
 hWrite=NULL;
 MessageBox("创建子进程失败！");
 return;
}
else
{
 CloseHandle(pi.hProcess);
 CloseHandle(pi.hThread);
}
}

菜单“读取数据”代码

void CParentView::OnPipeRead()
{
// TOD Add your command handler code here
char buf[100];
DWORD dwRead;
if(!ReadFile(hRead,buf,100,&dwRead,NULL))
{
 MessageBox("读取数据失败！");
 return;
}
MessageBox(buf);
}
 
void CParentView::OnPipeWrite() 菜单“写入数据”代码
{
// TOD Add your command handler code here
char buf[]="http://www.sunxin.org";
DWORD dwWrite;
if(!WriteFile(hWrite,buf,strlen(buf)+1,&dwWrite,NULL))
{
 MessageBox("写入数据失败！");
 return;
}
}

d.再建一个Child的单文档，在View中增加两个成员hRead和hWrite.在OnInitialUpdate()中得到句柄的值。

void CChildView::OnInitialUpdate()
{
CView::OnInitialUpdate();
 
// TOD Add your specialized code here and/or call the base class
hRead=GetStdHandle(STD_INPUT_HANDLE);注意这句代码！
hWrite=GetStdHandle(STD_OUTPUT_HANDLE);
}

e.加菜单“读取数据”“写入数据”其代码如下：

void CChildView::OnPipeRead()
{
// TOD Add your command handler code here
char buf[100];
DWORD dwRead;
if(!ReadFile(hRead,buf,100,&dwRead,NULL))
{
 MessageBox("读取数据失败！");
 return;
}
MessageBox(buf);
}
 
void CChildView::OnPipeWrite()
{
// TOD Add your command handler code here
char buf[]="匿名管道测试程序";
DWORD dwWrite;
if(!WriteFile(hWrite,buf,strlen(buf)+1,&dwWrite,NULL))
{
 MessageBox("写入数据失败！");
 return;
}
}

3.命名管道：还可以跨网络通信，服务器只能在win2000和NT下运行！而客户端可以在95下运行。关键函数CreateNamedPipe

 a.先建一个NamedPipeSRV单文档应用程序，加菜单“创建管道”“读取数据”“写入数据”

 b.在View中增加Handle变量hPipe，注意在析构函数中释放它！

 c.响应菜单，创建命名管道

void CNamedPipeSrvView::OnPipeCreate()
{
// TOD Add your command handler code here
hPipe=CreateNamedPipe("\\\\.\\pipe\\MyPipe",
 PIPE_ACCESS_DUPLEX | FILE_FLAG_OVERLAPPED,
 0,1,1024,1024,0,NULL);
if(INVALID_HANDLE_VALUE==hPipe)
{
 MessageBox("创建命名管道失败！");
 hPipe=NULL;
 return;
}
HANDLE hEvent;
hEvent=CreateEvent(NULL,TRUE,FALSE,NULL);
if(!hEvent)
{
 MessageBox("创建事件对象失败！");
 CloseHandle(hPipe);
 hPipe=NULL;
 return;
}
OVERLAPPED ovlap;
ZeroMemory(&ovlap,sizeof(OVERLAPPED));
ovlap.hEvent=hEvent;
if(!ConnectNamedPipe(hPipe,&ovlap))
{
 if(ERROR_IO_PENDING!=GetLastError())
 {
   MessageBox("等待客户端连接失败！");
   CloseHandle(hPipe);
   CloseHandle(hEvent);
   hPipe=NULL;
   return;
 }
}
if(WAIT_FAILED==WaitForSingleObject(hEvent,INFINITE))
{
 MessageBox("等待对象失败！");
 CloseHandle(hPipe);
 CloseHandle(hEvent);
 hPipe=NULL;
 return;
}
CloseHandle(hEvent);
}

void CNamedPipeSrvView::OnPipeRead()
{
// TOD Add your command handler code here
char buf[100];
DWORD dwRead;
if(!ReadFile(hPipe,buf,100,&dwRead,NULL))
{
 MessageBox("读取数据失败！");
 return;
}
MessageBox(buf);
}
 
void CNamedPipeSrvView::OnPipeWrite()
{
// TOD Add your command handler code here
char buf[]="http://www.sunxin.org";
DWORD dwWrite;
if(!WriteFile(hPipe,buf,strlen(buf)+1,&dwWrite,NULL))
{
 MessageBox("写入数据失败！");
 return;
}
}
 

 d.再建一个NamedPipeCLT单文档工程，加菜单“连接管道”“读取数据”“写入数据”，当然别忘记成员变量hPipe的定义和初始化

      e.响应菜单代码

void CNamedPipeCltView::OnPipeConnect() 连接管道
{
// TOD Add your command handler code here
if(!WaitNamedPipe("\\\\.\\pipe\\MyPipe",NMPWAIT_WAIT_FOREVER))
{
 MessageBox("当前没有可利用的命名管道实例！");
 return;
}
hPipe=CreateFile("\\\\.\\pipe\\MyPipe",GENERIC_READ | GENERIC_WRITE,
 0,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,NULL);
if(INVALID_HANDLE_VALUE==hPipe)
{
 MessageBox("打开命名管道失败！");
 hPipe=NULL;
 return;
}
}
 
void CNamedPipeCltView::OnPipeRead() 读取数据
{
// TOD Add your command handler code here
char buf[100];
DWORD dwRead;
if(!ReadFile(hPipe,buf,100,&dwRead,NULL))
{
 MessageBox("读取数据失败！");
 return;
}
MessageBox(buf);
}
 
void CNamedPipeCltView::OnPipeWrite() 写入数据
{
// TOD Add your command handler code here
char buf[]="命名管道测试程序";
DWORD dwWrite;
if(!WriteFile(hPipe,buf,strlen(buf)+1,&dwWrite,NULL))
{
 MessageBox("写入数据失败！");
 return;
}
}

4.邮槽，使用时应将消息长度限制在424字节以下，关键函数CreateMailSlot()
 a.先建一个MailSlotSRV工程，加菜单“接收数据”
 b.消息响应代码：
菜单“接收数据”的代码
void CMailslotSrvView::OnMailslotRecv()
{
// TOD Add your command handler code here
HANDLE hMailslot;
hMailslot=CreateMailslot("\\\\.\\mailslot\\MyMailslot",0,
 MAILSLOT_WAIT_FOREVER,NULL);
if(INVALID_HANDLE_VALUE==hMailslot)
{
 MessageBox("创建油槽失败！");
 return;
}
char buf[100];
DWORD dwRead;
if(!ReadFile(hMailslot,buf,100,&dwRead,NULL))
{
 MessageBox("读取数据失败！");
 CloseHandle(hMailslot);
 return;
}
MessageBox(buf);
CloseHandle(hMailslot);
}

c.加工程MailSlotCLT,加菜单“发送数据”

d.加消息响应，添加代码，客户端也比较简单。

void CMailslotCltView::OnMailslotSend() 菜单“发送数据”的代码
{
// TOD Add your command handler code here
HANDLE hMailslot;
hMailslot=CreateFile("\\\\.\\mailslot\\MyMailslot",GENERIC_WRITE,
 FILE_SHARE_READ,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,NULL);
if(INVALID_HANDLE_VALUE==hMailslot)
{
 MessageBox("打开油槽失败！");
 return;
}
char buf[]="http://www.sunxin.org";
DWORD dwWrite;
if(!WriteFile(hMailslot,buf,strlen(buf)+1,&dwWrite,NULL))
{
 MessageBox("写入数据失败！");
 CloseHandle(hMailslot);
 return;
}
CloseHandle(hMailslot);
}

5.以上4种方法各有优缺点：剪贴板比较简单。邮槽是基于广播的，可以一对多发送。但只能一个发送，一个接收，要想同时发送接收，须写两次代码。

命名管道和邮槽可以进行网络通信。