使用完成例程的命名管道服务器
以下示例是创建消息类型管道并使用重叠操作的单线程管道服务器。 它使用扩展函数 ReadFileEx 和 WriteFileEx 通过完成例程执行重叠 I/O，该例程在操作完成后排队等待执行。 管道服务器使用 WaitForSingleObjectEx 函数，该函数执行可警报的等待操作，该操作在完成例程准备好执行时返回。 当向事件对象发出信号时，wait 函数也会返回 ，在此示例中指示重叠的 ConnectNamedPipe 操作已完成 (新客户端已连接) 。 此管道服务器可与命名管道客户端中所述的 管道客户端一起使用。
最初，管道服务器创建管道的单个实例，并启动重叠的 ConnectNamedPipe 操作。 当客户端连接时，服务器分配一个结构来为该管道实例提供存储，然后调用 ReadFileEx 函数以启动一系列 I/O 操作来处理与客户端的通信。 每个操作指定一个完成例程，该例程在序列中执行下一个操作。 当客户端断开连接且管道实例关闭时，序列终止。 为新客户端启动操作序列后，服务器将创建另一个管道实例，并等待下一个客户端连接。
ReadFileEx 和 WriteFileEx 函数的参数指定完成例程和指向 OVERLAPPED 结构的指针。 此指针将传递到其 lpOverLap 参数中的完成例程。 由于 OVERLAPPED 结构指向为每个管道实例分配的结构中的第一个成员，因此完成例程可以使用其 lpOverLap 参数访问管道实例的结构。
#include <windows.h>
#include <stdio.h>
#include <tchar.h>
#include <strsafe.h>
#define PIPE_TIMEOUT 5000
#define BUFSIZE 4096
typedef struct
{
OVERLAPPED oOverlap;
HANDLE hPipeInst;
TCHAR chRequest[BUFSIZE];
DWORD cbRead;
TCHAR chReply[BUFSIZE];
DWORD cbToWrite;
} PIPEINST, *LPPIPEINST;
VOID DisconnectAndClose(LPPIPEINST);
BOOL CreateAndConnectInstance(LPOVERLAPPED);
BOOL ConnectToNewClient(HANDLE, LPOVERLAPPED);
VOID GetAnswerToRequest(LPPIPEINST);
VOID WINAPI CompletedWriteRoutine(DWORD, DWORD, LPOVERLAPPED);
VOID WINAPI CompletedReadRoutine(DWORD, DWORD, LPOVERLAPPED);
HANDLE hPipe;
int _tmain(VOID)
{
HANDLE hConnectEvent;
OVERLAPPED oConnect;
LPPIPEINST lpPipeInst;
DWORD dwWait, cbRet;
BOOL fSuccess, fPendingIO;
// Create one event object for the connect operation.
hConnectEvent = CreateEvent(
NULL, // default security attribute
TRUE, // manual reset event
TRUE, // initial state = signaled
NULL); // unnamed event object
if (hConnectEvent == NULL)
{
printf("CreateEvent failed with %d.\n", GetLastError());
return 0;
}
oConnect.hEvent = hConnectEvent;
// Call a subroutine to create one instance, and wait for
// the client to connect.
fPendingIO = CreateAndConnectInstance(&oConnect);
while (1)
{
// Wait for a client to connect, or for a read or write
// operation to be completed, which causes a completion
// routine to be queued for execution.
dwWait = WaitForSingleObjectEx(
hConnectEvent, // event object to wait for
INFINITE, // waits indefinitely
TRUE); // alertable wait enabled
switch (dwWait)
{
// The wait conditions are satisfied by a completed connect
// operation.
case 0:
// If an operation is pending, get the result of the
// connect operation.
if (fPendingIO)
{
fSuccess = GetOverlappedResult(
hPipe, // pipe handle
&oConnect, // OVERLAPPED structure
&cbRet, // bytes transferred
FALSE); // does not wait
if (!fSuccess)
{
printf("ConnectNamedPipe (%d)\n", GetLastError());
return 0;
}
}
// Allocate storage for this instance.
lpPipeInst = (LPPIPEINST) GlobalAlloc(
GPTR, sizeof(PIPEINST));
if (lpPipeInst == NULL)
{
printf("GlobalAlloc failed (%d)\n", GetLastError());
return 0;
}
lpPipeInst->hPipeInst = hPipe;
// Start the read operation for this client.
// Note that this same routine is later used as a
// completion routine after a write operation.
lpPipeInst->cbToWrite = 0;
CompletedWriteRoutine(0, 0, (LPOVERLAPPED) lpPipeInst);
// Create new pipe instance for the next client.
fPendingIO = CreateAndConnectInstance(
&oConnect);
break;
// The wait is satisfied by a completed read or write
// operation. This allows the system to execute the
// completion routine.
case WAIT_IO_COMPLETION:
break;
// An error occurred in the wait function.
default:
{
printf("WaitForSingleObjectEx (%d)\n", GetLastError());
return 0;
}
}
}
return 0;
}
// CompletedWriteRoutine(DWORD, DWORD, LPOVERLAPPED)
// This routine is called as a completion routine after writing to
// the pipe, or when a new client has connected to a pipe instance.
// It starts another read operation.
VOID WINAPI CompletedWriteRoutine(DWORD dwErr, DWORD cbWritten,
LPOVERLAPPED lpOverLap)
{
LPPIPEINST lpPipeInst;
BOOL fRead = FALSE;
// lpOverlap points to storage for this instance.
lpPipeInst = (LPPIPEINST) lpOverLap;
// The write operation has finished, so read the next request (if
// there is no error).
if ((dwErr == 0) && (cbWritten == lpPipeInst->cbToWrite))
fRead = ReadFileEx(
lpPipeInst->hPipeInst,
lpPipeInst->chRequest,
BUFSIZE*sizeof(TCHAR),
(LPOVERLAPPED) lpPipeInst,
(LPOVERLAPPED_COMPLETION_ROUTINE) CompletedReadRoutine);
// Disconnect if an error occurred.
if (! fRead)
DisconnectAndClose(lpPipeInst);
}
// CompletedReadRoutine(DWORD, DWORD, LPOVERLAPPED)
// This routine is called as an I/O completion routine after reading
// a request from the client. It gets data and writes it to the pipe.
VOID WINAPI CompletedReadRoutine(DWORD dwErr, DWORD cbBytesRead,
LPOVERLAPPED lpOverLap)
{
LPPIPEINST lpPipeInst;
BOOL fWrite = FALSE;
// lpOverlap points to storage for this instance.
lpPipeInst = (LPPIPEINST) lpOverLap;
// The read operation has finished, so write a response (if no
// error occurred).
if ((dwErr == 0) && (cbBytesRead != 0))
{
GetAnswerToRequest(lpPipeInst);
fWrite = WriteFileEx(
lpPipeInst->hPipeInst,
lpPipeInst->chReply,
lpPipeInst->cbToWrite,
(LPOVERLAPPED) lpPipeInst,
(LPOVERLAPPED_COMPLETION_ROUTINE) CompletedWriteRoutine);
}
// Disconnect if an error occurred.
if (! fWrite)
DisconnectAndClose(lpPipeInst);
}
// DisconnectAndClose(LPPIPEINST)
// This routine is called when an error occurs or the client closes
// its handle to the pipe.
VOID DisconnectAndClose(LPPIPEINST lpPipeInst)
{
// Disconnect the pipe instance.
if (! DisconnectNamedPipe(lpPipeInst->hPipeInst) )
{
printf("DisconnectNamedPipe failed with %d.\n", GetLastError());
}
// Close the handle to the pipe instance.
CloseHandle(lpPipeInst->hPipeInst);
// Release the storage for the pipe instance.
if (lpPipeInst != NULL)
GlobalFree(lpPipeInst);
}
// CreateAndConnectInstance(LPOVERLAPPED)
// This function creates a pipe instance and connects to the client.
// It returns TRUE if the connect operation is pending, and FALSE if
// the connection has been completed.
BOOL CreateAndConnectInstance(LPOVERLAPPED lpoOverlap)
{
LPTSTR lpszPipename = TEXT("\\\\.\\pipe\\mynamedpipe");
hPipe = CreateNamedPipe(
lpszPipename, // pipe name
PIPE_ACCESS_DUPLEX | // read/write access
FILE_FLAG_OVERLAPPED, // overlapped mode
PIPE_TYPE_MESSAGE | // message-type pipe
PIPE_READMODE_MESSAGE | // message read mode
PIPE_WAIT, // blocking mode
PIPE_UNLIMITED_INSTANCES, // unlimited instances
BUFSIZE*sizeof(TCHAR), // output buffer size
BUFSIZE*sizeof(TCHAR), // input buffer size
PIPE_TIMEOUT, // client time-out
NULL); // default security attributes
if (hPipe == INVALID_HANDLE_VALUE)
{
printf("CreateNamedPipe failed with %d.\n", GetLastError());
return 0;
}
// Call a subroutine to connect to the new client.
return ConnectToNewClient(hPipe, lpoOverlap);
}
BOOL ConnectToNewClient(HANDLE hPipe, LPOVERLAPPED lpo)
{
BOOL fConnected, fPendingIO = FALSE;
// Start an overlapped connection for this pipe instance.
fConnected = ConnectNamedPipe(hPipe, lpo);
// Overlapped ConnectNamedPipe should return zero.
if (fConnected)
{
printf("ConnectNamedPipe failed with %d.\n", GetLastError());
return 0;
}
switch (GetLastError())
{
// The overlapped connection in progress.
case ERROR_IO_PENDING:
fPendingIO = TRUE;
break;
// Client is already connected, so signal an event.
case ERROR_PIPE_CONNECTED:
if (SetEvent(lpo->hEvent))
break;
// If an error occurs during the connect operation...
default:
{
printf("ConnectNamedPipe failed with %d.\n", GetLastError());
return 0;
}
}
return fPendingIO;
}
VOID GetAnswerToRequest(LPPIPEINST pipe)
{
_tprintf( TEXT("[%d] %s\n"), pipe->hPipeInst, pipe->chRequest);
StringCchCopy( pipe->chReply, BUFSIZE, TEXT("Default answer from server") );
pipe->cbToWrite = (lstrlen(pipe->chReply)+1)*sizeof(TCHAR);
}
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