问题描述
我已经编写了一个用于处理命名管道连接的类，如果创建了一个实例，请关闭它，然后尝试创建另一个实例，对CreateFile()的调用将返回INVALID_HANDLE_VALUE，而GetLastError()的调用将返回ERROR_PIPE_BUSY .这里发生了什么?如何确保对Connect()的调用成功?
I have written a class to handle named pipe connections, and if I create an instance, close it, and then try to create another instance the call to CreateFile() returns INVALID_HANDLE_VALUE, and GetLastError() returns ERROR_PIPE_BUSY. What's going on here? What can I do to insure the call to Connect() succeeds?
PipeAsync A, B;
A.Connect("\\\\.\\pipe\\test",5000);
A.Close();
cout << GetLastError(); // some random value
B.Connect("\\\\.\\pipe\\test",5000);
cout << GetLastError(); // 231 (ERROR_PIPE_BUSY)
B.Close();
这是我Connect()和Close()
BOOL PipeAsync::Connect(LPCSTR pszPipeName, DWORD dwTimeout)
{
this->pszPipeName = pszPipeName;
this->fExisting = TRUE;
DWORD dwMode = this->fMessageMode ? PIPE_READMODE_MESSAGE : PIPE_READMODE_BYTE;
hPipe = CreateFile(
this->pszPipeName,
GENERIC_READ | GENERIC_WRITE,
0,
NULL,
OPEN_EXISTING,
FILE_FLAG_OVERLAPPED,
NULL);
if( INVALID_HANDLE_VALUE == hPipe )
return FALSE; /* set break point here ; breaks here on second call to Connect() */
if( GetLastError() == ERROR_PIPE_BUSY )
if(!WaitNamedPipe( this->pszPipeName, dwTimeout ))
return FALSE; /* set break point here */
if( !SetNamedPipeHandleState( hPipe, &dwMode, NULL, NULL ) )
return FALSE; /* set break point here */
return TRUE;
}
VOID PipeAsync::Close()
{
if( fExisting )
DisconnectNamedPipe( hPipe );
CloseHandle( hPipe );
}
编辑:我忘了告诉你我是如何得出结论的...我设置了注释中指示的断点.运行时，它将在第一个断点处停止.
I forgot to tell you how I concluded this... I set break points indicated in the comments. When run, it stops on the first break point.
编辑:这是我更新的代码
if( INVALID_HANDLE_VALUE == hPipe )
if( GetLastError() == ERROR_PIPE_BUSY )
{
if(!WaitNamedPipe( this->pszPipeName, dwTimeout ))
return FALSE; /* break-point: breaks here on second call */
}
else
return FALSE; /* break-point /*
现在，WaitNamedPipe()在第二次调用Connect()时返回false，而GetLastError()返回2，或者ERROR_FILE_NOT_FOUND吗?
Now, WaitNamedPipe() is returning false on the second call to Connect() and GetLastError() is returning 2, or ERROR_FILE_NOT_FOUND ?
推荐答案
来自命名管道客户端:
链接中包含处理ERROR_PIPE_BUSY的示例代码.
The link has example code on coping with ERROR_PIPE_BUSY.
一个小的可编译示例，演示了在命名管道上的接受和连接:
Small compilable example that demonstrates accepting and connecting on a named pipe:
const char* const PIPE_NAME = "\\\\.\\pipe\\test";
const int MAX_CONNECTIONS = 10;
void client_main()
{
DWORD last_error;
unsigned int elapsed_seconds = 0;
const unsigned int timeout_seconds = 5;
HANDLE handle = CreateFile(PIPE_NAME,
GENERIC_READ | GENERIC_WRITE,
0,
0,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
0);
while (INVALID_HANDLE_VALUE == handle &&
elapsed_seconds < timeout_seconds)
{
last_error = GetLastError();
if (last_error != ERROR_PIPE_BUSY)
{
break;
}
Sleep(1 * 1000);
elapsed_seconds++;
handle = CreateFile(PIPE_NAME,
GENERIC_READ | GENERIC_WRITE,
0,
0,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
0);
}
if (INVALID_HANDLE_VALUE == handle)
{
std::cerr << "Failed to connect to pipe " << PIPE_NAME <<
": last_error=" << last_error << "\n";
}
else
{
std::cout << "Connected to pipe " << PIPE_NAME << "\n";
CloseHandle(handle);
}
}
HANDLE _get_server_handle()
{
// Error handling omitted for security descriptor creation.
SECURITY_DESCRIPTOR sd;
InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION);
SetSecurityDescriptorDacl(&sd, TRUE, static_cast<PACL>(0), FALSE);
SECURITY_ATTRIBUTES sa;
sa.nLength = sizeof(sa);
sa.lpSecurityDescriptor = &sd;
sa.bInheritHandle = FALSE;
// Create a bi-directional message pipe.
HANDLE handle = CreateNamedPipe(PIPE_NAME,
PIPE_ACCESS_DUPLEX,
PIPE_TYPE_MESSAGE |
PIPE_READMODE_MESSAGE |
PIPE_NOWAIT,
PIPE_UNLIMITED_INSTANCES,
4096,
4096,
0,
&sa);
if (INVALID_HANDLE_VALUE == handle)
{
std::cerr << "Failed to create named pipe handle: last_error=" <<
GetLastError() << "\n";
}
return handle;
}
void server_main()
{
HANDLE handle = _get_server_handle();
if (INVALID_HANDLE_VALUE != handle)
{
int count = 0;
while (count < MAX_CONNECTIONS)
{
BOOL result = ConnectNamedPipe(handle, 0);
const DWORD last_error = GetLastError();
if (ERROR_NO_DATA == last_error)
{
count++;
std::cout << "A client connected and disconnected: count=" <<
count << "\n";
CloseHandle(handle);
handle = _get_server_handle();
}
else if (ERROR_PIPE_CONNECTED == last_error)
{
count++;
std::cout << "A client connected before call to " <<
"ConnectNamedPipe(): count=" << count << "\n";
CloseHandle(handle);
handle = _get_server_handle();
}
else if (ERROR_PIPE_LISTENING != last_error)
{
std::cerr << "Failed to wait for connection: last_error=" <<
GetLastError() << "\n";
CloseHandle(handle);
break;
}
Sleep(100);
}
}
}
int main(int a_argc, char** a_argv)
{
if (2 == a_argc)
{
if (std::string("client") == *(a_argv + 1))
{
for (int i = 0; i < MAX_CONNECTIONS; i++)
{
client_main();
}
}
else if (std::string("server") == *(a_argv + 1))
{
server_main();
}
}
return 0;
}
首先执行服务器端:
pipetest.exe server
然后执行客户端:
pipetest.exe client
我无法从发布的代码中分辨出问题所在.希望这个小例子可以帮助您找到问题所在.
I could not tell what the problem was from the posted code. Hopefully this small example will assist you in finding the issue.
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