[英]Problem reconnecting to the named pipe
我有一個命名管道服務器和客戶端。 (在VC ++中執行此操作)。
服務器呢
客戶呢
執行順序如下,
這是第一次正常工作。 但是,當客戶端嘗試第二次連接時會出現問題。 當客戶端在服務器執行ConnectNamedPipe 之前第二次嘗試連接(CreateFile)時(但在 disconnectnamedpipe 之后 ),它將獲得ERROR_PIPE_BUSY。 如果客戶端在服務器調用ConnectNamedPipe后調用createfile,則它可以工作。
無論如何,我可以在服務器調用ConnectNamedPipe之前連接客戶端(CreateFile)(在DisconnectNamedPipe之后)?
服務器代碼:
pipe_handle.pipe = CreateNamedPipe(TEXT("\\\\.\\pipe\\testpipe1"),
PIPE_ACCESS_OUTBOUND |
FILE_FLAG_OVERLAPPED, // read/write access
PIPE_TYPE_MESSAGE | // message type pipe
PIPE_READMODE_MESSAGE | // message-read mode
PIPE_WAIT, // blocking mode
PIPE_UNLIMITED_INSTANCES, // max. instances
BUFFER_SIZE, // output buffer size
BUFFER_SIZE, // input buffer size
2000, // client time-out
NULL);
if (pipe_handle.pipe == INVALID_HANDLE_VALUE) {
std::cout << "Error while creating pipe" << std::endl;
return -1;
}
std::cout <<"Connecting to named pipe" << std::endl;
std::cout<< "Somebody connected to named pipe" << std::endl;
int ac;
for (ac=0; ac<2; ac++) {
char a[25];
// Wait for some input. This helps me to start the client in other terminal.
cin >> a;
cout << "Connecting..." << endl;
ConnectNamedPipe(pipe_handle.pipe, 0);
cout << "Connect pipe returned." << endl;
// Wait for some input.
cin >> a;
string message = "Test message";
DWORD bytes_written;
if (!WriteFile(pipe_handle.pipe, message.c_str(), message.size(),
&bytes_written, NULL)) {
DWORD er = GetLastError();
char errs[200];
sprintf(errs, "Error : %ld", er);
std::cout << "Error communicating to client.";
std::cout << errs;
}
std::cout << "Written to pipe";
FlushFileBuffers(pipe_handle.pipe);
if (!DisconnectNamedPipe(pipe_handle.pipe)) {
std::cout << "Disconnect failed"<< GetLastError() << endl;
} else {
std::cout << "Disconnect successful"<<endl;
}
}
客戶代碼:
while (1) {
std::cout << "Returned" << std::endl;
hPipe = CreateFile(
lpszPipename, // pipe name
GENERIC_READ,
0, // no sharing
NULL, // default security attributes
OPEN_EXISTING, // opens existing pipe
FILE_FLAG_OVERLAPPED, // default attributes
NULL); // no template file
// Break if the pipe handle is valid.
if (hPipe != INVALID_HANDLE_VALUE)
break;
// Exit if an error other than ERROR_PIPE_BUSY occurs.
if (GetLastError() != ERROR_PIPE_BUSY) {
std::cout<< "Could not open pipe " << GetLastError() << std::endl;
return -1;
}
// All pipe instances are busy, so wait for sometime.
if ( ! WaitNamedPipe(lpszPipename, NMPWAIT_USE_DEFAULT_WAIT)) {
std::cout<< "Could not open pipe: wait timed out." << std::endl;
}
}
OVERLAPPED ol1;
memset(&ol1, 0, sizeof(ol1));
ol1.Offset = 0;
ol1.OffsetHigh = 0;
ol1.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
HANDLE events[1];
events[0] = ol1.hEvent;
cbToWrite = (lstrlen(message)+1)*sizeof(TCHAR);
DWORD bytes_to_read = 2000;
char * buf = reinterpret_cast<char *>(malloc(bytes_to_read));
DWORD bytes_read;
std::cout << "Waiting for read" << std::endl;
bool a = ReadFile(hPipe, buf, bytes_to_read, &bytes_read, &ol1);
if ( ! fSuccess) {
std::cout << "WriteFile to pipe failed. GLE " << GetLastError() << std::endl;
}
std::cout << "Waiting for multiple objects" << std::endl;
WaitForMultipleObjects(1, events, FALSE, INFINITE);
std::cout << "multiple objects returned" << std::endl;
printf("\nMessage sent to server");
CancelIo(hPipe);
CloseHandle(hPipe);
如果在客戶端的CreateFile()調用上獲得ERROR_PIPE_BUSY,則需要調用WaitNamedPipe(),然后在返回時重試。 如果從WaitNamedPipe()返回零,這意味着它在沒有管道可用的情況下超時。 如果您將NMPWAIT_WAIT_FOREVER作為超時傳遞,您將永遠不會看到這種情況。
您還需要記住,在WaitNamedPipe()返回和調用CreateFile()之間,管道可能會再次忙碌; 因此,你需要在循環中完成它。 像這樣:
while (true)
{
hPipe = CreateFile(pipeName,
GENERIC_READ | GENERIC_WRITE,
0,
0,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
0);
if (hPipe == INVALID_HANDLE_VALUE)
{
if (GetLastError() == ERROR_PIPE_BUSY)
{
if (!WaitNamedPipe(pipeName, NMPWAIT_USE_DEFAULT_WAIT))
continue; // timeout, try again
}
else
return false; // error
}
else
break; // success
}
編輯:
我簡化了你的代碼,現在它工作正常。 工作服務器和客戶端跟隨。
服務器:
#include <windows.h>
#include <stdio.h>
int main(void)
{
HANDLE pipe;
const DWORD BUFFER_SIZE = 1024;
pipe = CreateNamedPipe("\\\\.\\pipe\\testpipe1",
PIPE_ACCESS_OUTBOUND |
FILE_FLAG_OVERLAPPED, // read/write access
PIPE_TYPE_MESSAGE | // message type pipe
PIPE_READMODE_MESSAGE | // message-read mode
PIPE_WAIT, // blocking mode
PIPE_UNLIMITED_INSTANCES, // max. instances
BUFFER_SIZE, // output buffer size
BUFFER_SIZE, // input buffer size
2000, // client time-out
NULL);
if (pipe == INVALID_HANDLE_VALUE)
{
printf("Error while creating pipe\n");
return -1;
}
printf("Connecting to named pipe\n");
int ac;
for (ac=0; ac<2; ac++)
{
// Wait for some input. This helps me to start the client in other terminal.
printf("Connecting...\n");
ConnectNamedPipe(pipe, 0);
printf("Connect pipe returned.\n");
// Wait for some input.
char * message = "Test message";
DWORD bytes_written;
if (!WriteFile(pipe, message, strlen(message)+1, &bytes_written, NULL))
{
DWORD er = GetLastError();
char errs[200];
sprintf_s(errs, "Error : %ld", er);
printf("Error communicating to client.\n");
printf(errs);
}
printf("Written to pipe\n");
FlushFileBuffers(pipe);
if (!DisconnectNamedPipe(pipe))
{
printf("Disconnect failed %d\n", GetLastError());
}
else
{
printf("Disconnect successful\n");
}
}
}
客戶:
#include <windows.h>
#include <stdio.h>
int main(void)
{
HANDLE hPipe;
while (1)
{
printf("Returned\n");
hPipe = CreateFile("\\\\.\\pipe\\testpipe1",
GENERIC_READ,
0, // no sharing
NULL, // default security attributes
OPEN_EXISTING, // opens existing pipe
0, // default attributes
NULL); // no template file
// Break if the pipe handle is valid.
if (hPipe != INVALID_HANDLE_VALUE)
break;
// Exit if an error other than ERROR_PIPE_BUSY occurs.
if (GetLastError() != ERROR_PIPE_BUSY)
{
printf("Could not open pipe %d\n", GetLastError());
return -1;
}
// All pipe instances are busy, so wait for sometime.
if ( ! WaitNamedPipe("\\\\.\\pipe\\testpipe1", NMPWAIT_USE_DEFAULT_WAIT))
{
printf("Could not open pipe: wait timed out.\n");
}
}
char *message = "hello";
DWORD cbToWrite = (strlen(message)+1)*sizeof(message[0]);
DWORD bytes_to_read = 2000;
char * buf = reinterpret_cast<char *>(malloc(bytes_to_read));
DWORD bytes_read;
printf("Waiting for read\n");
bytes_read = 0;
ReadFile(hPipe, buf, bytes_to_read, &bytes_read, 0);
if (bytes_read <= 0)
{
printf("ReadFile from pipe failed. GLE \n");
}
else
printf("Read %d bytes: %s\n", bytes_read, buf);
CloseHandle(hPipe);
return 0;
}
在服務器端,當您決定斷開連接時,您必須使用鏈:
1)CloseHandle(管道);
2)DisconnectNamedPipe(Pipe);
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