Servidor de canalización con nombre mediante rutinas de finalización
El ejemplo siguiente es un servidor de canalización de un solo subproceso que crea una canalización de tipo de mensaje y usa operaciones superpuestas. Usa las funciones extendidas ReadFileEx y WriteFileEx para realizar E/S superpuestas mediante una rutina de finalización, que se pone en cola para su ejecución cuando finaliza la operación. El servidor de canalización usa la función WaitForSingleObjectEx , que realiza una operación de espera alertable que devuelve cuando una rutina de finalización está lista para ejecutarse. La función wait también devuelve cuando se señala un objeto de evento, que en este ejemplo indica que la operación ConnectNamedPipe superpuesta ha finalizado (un nuevo cliente se ha conectado). Este servidor de canalización se puede usar con el cliente de canalización descrito en Cliente de canalización con nombre.
Inicialmente, el servidor de canalización crea una única instancia de la canalización e inicia una operación ConnectNamedPipe superpuesta. Cuando un cliente se conecta, el servidor asigna una estructura para proporcionar almacenamiento para esa instancia de canalización y, a continuación, llama a la función ReadFileEx para iniciar una secuencia de operaciones de E/S para controlar las comunicaciones con el cliente. Cada operación especifica una rutina de finalización que realiza la siguiente operación en la secuencia. La secuencia finaliza cuando el cliente está desconectado y se cierra la instancia de canalización. Después de iniciar la secuencia de operaciones para el nuevo cliente, el servidor crea otra instancia de canalización y espera a que el siguiente cliente se conecte.
Los parámetros de las funciones ReadFileEx y WriteFileEx especifican una rutina de finalización y un puntero a una estructura SUPERPUESTA . Este puntero se pasa a la rutina de finalización en su parámetro lpOverLap . Dado que la estructura SUPERPUESTA apunta al primer miembro de la estructura asignada para cada instancia de canalización, la rutina de finalización puede usar su parámetro lpOverLap para acceder a la estructura de la instancia de canalización.
#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);
}
Temas relacionados