Note that nonblocking mode is supported for compatibility with Microsoft LAN Manager version 2.0 and should not be used to achieve asynchronous I/O with named pipes. For more information on asynchronous pipe I/O, see Synchronous and Overlapped Input and Output.

One of the following remote-client modes can be specified. Different instances of the same pipe can specify different remote-client modes.

The maximum number of instances that can be created for this pipe. The first instance of the pipe can specify this value; the same number must be specified for other instances of the pipe. Acceptable values are in the range 1 through PIPE_UNLIMITED_INSTANCES (255).

If this parameter is PIPE_UNLIMITED_INSTANCES, the number of pipe instances that can be created is limited only by the availability of system resources. If nMaxInstances is greater than PIPE_UNLIMITED_INSTANCES, the return value is INVALID_HANDLE_VALUE and GetLastError returns ERROR_INVALID_PARAMETER.

The number of bytes to reserve for the output buffer. For a discussion on sizing named pipe buffers, see the following Remarks section.

The number of bytes to reserve for the input buffer. For a discussion on sizing named pipe buffers, see the following Remarks section.

The default time-out value, in milliseconds, if the WaitNamedPipe function specifies NMPWAIT_USE_DEFAULT_WAIT. Each instance of a named pipe must specify the same value.

A value of zero will result in a default time-out of 50 milliseconds.

A pointer to a SECURITY_ATTRIBUTES structure that specifies a security descriptor for the new named pipe and determines whether child processes can inherit the returned handle. If lpSecurityAttributes is NULL, the named pipe gets a default security descriptor and the handle cannot be inherited. The ACLs in the default security descriptor for a named pipe grant full control to the LocalSystem account, administrators, and the creator owner. They also grant read access to members of the Everyone group and the anonymous account.

Return value

If the function succeeds, the return value is a handle to the server end of a named pipe instance.

If the function fails, the return value is INVALID_HANDLE_VALUE. To get extended error information, call GetLastError.

Remarks

To create an instance of a named pipe by using CreateNamedPipe, the user must have FILE_CREATE_PIPE_INSTANCE access to the named pipe object. If a new named pipe is being created, the access control list (ACL) from the security attributes parameter defines the discretionary access control for the named pipe.

All instances of a named pipe must specify the same pipe type (byte-type or message-type), pipe access (duplex, inbound, or outbound), instance count, and time-out value. If different values are used, this function fails and GetLastError returns ERROR_ACCESS_DENIED.

A client process connects to a named pipe by using the CreateFile or CallNamedPipe function. The client side of a named pipe starts out in byte mode, even if the server side is in message mode. To avoid problems receiving data, set the client side to message mode as well. To change the mode of the pipe, the pipe client must open a read-only pipe with GENERIC_READ and FILE_WRITE_ATTRIBUTES access.

The pipe server should not perform a blocking read operation until the pipe client has started. Otherwise, a race condition can occur. This typically occurs when initialization code, such as the C run-time, needs to lock and examine inherited handles.

Every time a named pipe is created, the system creates the inbound and/or outbound buffers using nonpaged pool, which is the physical memory used by the kernel. The number of pipe instances (as well as objects such as threads and processes) that you can create is limited by the available nonpaged pool. Each read or write request requires space in the buffer for the read or write data, plus additional space for the internal data structures.

The input and output buffer sizes are advisory. The actual buffer size reserved for each end of the named pipe is either the system default, the system minimum or maximum, or the specified size rounded up to the next allocation boundary. The buffer size specified should be small enough that your process will not run out of nonpaged pool, but large enough to accommodate typical requests.

Whenever a pipe write operation occurs, the system first tries to charge the memory against the pipe write quota. If the remaining pipe write quota is enough to fulfill the request, the write operation completes immediately. If the remaining pipe write quota is too small to fulfill the request, the system will try to expand the buffers to accommodate the data using nonpaged pool reserved for the process. The write operation will block until the data is read from the pipe so that the additional buffer quota can be released. Therefore, if your specified buffer size is too small, the system will grow the buffer as needed, but the downside is that the operation will block. If the operation is overlapped, a system thread is blocked; otherwise, the application thread is blocked.

To free resources used by a named pipe, the application should always close handles when they are no longer needed, which is accomplished either by calling the CloseHandle function or when the process associated with the instance handles ends. Note that an instance of a named pipe may have more than one handle associated with it. An instance of a named pipe is always deleted when the last handle to the instance of the named pipe is closed.

WindowsВ 10, version 1709:В В Pipes are only supported within an app-container; ie, from one UWP process to another UWP process that’s part of the same app. Also, named pipes must use the syntax «\.\pipe\LOCAL» for the pipe name.

Практическое руководство. Использование именованных каналов для сетевого взаимодействия между процессами How to: Use Named Pipes for Network Interprocess Communication

Именованные каналы обеспечивают межпроцессное взаимодействие между сервером канала и одним или несколькими клиентами канала. Named pipes provide interprocess communication between a pipe server and one or more pipe clients. Они предоставляют больше функциональных возможностей, чем анонимные каналы, которые обеспечивают межпроцессное взаимодействие на локальном компьютере. They offer more functionality than anonymous pipes, which provide interprocess communication on a local computer. Именованные каналы поддерживают полную дуплексную связь по сети и несколько экземпляров сервера, связь на основе сообщений и олицетворение клиента, позволяющее подключающимся процессам использовать собственные наборы разрешений на удаленных серверах. Named pipes support full duplex communication over a network and multiple server instances, message-based communication, and client impersonation, which enables connecting processes to use their own set of permissions on remote servers.

Для реализации именованных каналов используются классы NamedPipeServerStream и NamedPipeClientStream. To implement name pipes, use the NamedPipeServerStream and NamedPipeClientStream classes.

Пример Example

В примере ниже показано, как создать именованный канал с помощью класса NamedPipeServerStream. The following example demonstrates how to create a named pipe by using the NamedPipeServerStream class. В этом примере серверный процесс создает четыре потока. In this example, the server process creates four threads. Каждый поток может принимать подключение клиента. Each thread can accept a client connection. Процесс подключения клиента передает серверу имя файла. The connected client process then supplies the server with a file name. Если клиенту имеет необходимые разрешения, серверный процесс открывает указанный файл и отправляет клиенту его содержимое. If the client has sufficient permissions, the server process opens the file and sends its contents back to the client.

Пример Example

В примере ниже представлен клиентский процесс, основанный на классе NamedPipeClientStream. The following example shows the client process, which uses the NamedPipeClientStream class. Клиент подключается к серверному процессу и передает серверу имя файла. The client connects to the server process and sends a file name to the server. В этом примере используется олицетворение. Это означает, что у идентификатора, от имени которого выполняется клиентское приложение, должны быть разрешения на доступ к файлу. The example uses impersonation, so the identity that is running the client application must have permission to access the file. Затем сервер отправляет клиенту содержимое файла. The server then sends the contents of the file back to the client. Полученное содержимое файла выводится в консоль. The file contents are then displayed to the console.

Отказоустойчивость Robust Programming

Клиентский и серверный процессы в этом примере предназначены для выполнения на одном компьютере, поэтому объекту NamedPipeClientStream передается имя сервера «.» . The client and server processes in this example are intended to run on the same computer, so the server name provided to the NamedPipeClientStream object is «.» . Если клиентский и серверный процессы выполняются на разных компьютерах, вместо «.» должно быть указано сетевое имя компьютера, на котором осуществляется серверный процесс. If the client and server processes were on separate computers, «.» would be replaced with the network name of the computer that runs the server process.

Вам также может понравиться

Windows или Linux: Что лучше выбрать?

Есть много причин выбирать между Windows и Linux, но

Файл владелец изменить linux

Команда Chown в Linux Chown Command in Linux (File

Установка шлюза по умолчанию linux

Настройка сети вручную Содержание Краткое описание

Чем разбить диск для linux

ИТ База знаний Курс по Asterisk Полезно — Узнать IP —