subprocess.send(message[, sendHandle[, options]][, callback])

• message <Object>

• sendHandle <Handle> | <undefined> undefined、或 net.Socket、net.Server 或 dgram.Socket 对象。

  ¥sendHandle <Handle> | <undefined> undefined, or a net.Socket, net.Server, or dgram.Socket object.

• options <Object> options 参数（如果存在）是用于参数化某些类型句柄的发送的对象。options 支持以下属性：

  ¥options <Object> The options argument, if present, is an object used to parameterize the sending of certain types of handles. options supports the following properties:

  • keepOpen <boolean> 当传入 net.Socket 实例时可以使用的值。当为 true 时，套接字在发送过程中保持打开状态。默认值：false。

    ¥keepOpen <boolean> A value that can be used when passing instances of net.Socket. When true, the socket is kept open in the sending process. Default: false.

• callback <Function>

• 返回：<boolean>

  ¥Returns: <boolean>

当父进程和子进程之间建立了 IPC 通道时（即使用 child_process.fork() 时），可以使用 subprocess.send() 方法向子进程发送消息。当子进程是 Node.js 实例时，可以通过 'message' 事件接收这些消息。

¥When an IPC channel has been established between the parent and child processes ( i.e. when using child_process.fork()), the subprocess.send() method can be used to send messages to the child process. When the child process is a Node.js instance, these messages can be received via the 'message' event.

消息经过序列化和解析。结果消息可能与最初发送的消息不同。

¥The message goes through serialization and parsing. The resulting message might not be the same as what is originally sent.

例如，在父脚本中：

¥For example, in the parent script:

const { fork } = require('node:child_process');
const forkedProcess = fork(`${__dirname}/sub.js`);

forkedProcess.on('message', (message) => {
  console.log('PARENT got message:', message);
});

// Causes the child to print: CHILD got message: { hello: 'world' }
forkedProcess.send({ hello: 'world' });import { fork } from 'node:child_process';
const forkedProcess = fork(`${import.meta.dirname}/sub.js`);

forkedProcess.on('message', (message) => {
  console.log('PARENT got message:', message);
});

// Causes the child to print: CHILD got message: { hello: 'world' }
forkedProcess.send({ hello: 'world' });拷贝

然后子脚本 'sub.js' 可能如下所示：

¥And then the child script, 'sub.js' might look like this:

process.on('message', (message) => {
  console.log('CHILD got message:', message);
});

// Causes the parent to print: PARENT got message: { foo: 'bar', baz: null }
process.send({ foo: 'bar', baz: NaN }); 拷贝

子 Node.js 进程将拥有自己的 process.send() 方法，允许子进程将消息发送回父进程。

¥Child Node.js processes will have a process.send() method of their own that allows the child process to send messages back to the parent process.

发送 {cmd: 'NODE_foo'} 消息时有一种特殊情况。在 cmd 属性中包含 NODE_ 前缀的消息保留供在 Node.js 核心中使用，不会在子项的 'message' 事件中触发。相反，此类消息是使用 'internalMessage' 事件触发的，并由 Node.js 在内部使用。应用应避免使用此类消息或监听 'internalMessage' 事件，因为它可能会更改，恕不另行通知。

¥There is a special case when sending a {cmd: 'NODE_foo'} message. Messages containing a NODE_ prefix in the cmd property are reserved for use within Node.js core and will not be emitted in the child's 'message' event. Rather, such messages are emitted using the 'internalMessage' event and are consumed internally by Node.js. Applications should avoid using such messages or listening for 'internalMessage' events as it is subject to change without notice.

可以传递给 subprocess.send() 的可选 sendHandle 参数用于将 TCP 服务器或套接字对象传递给子进程。子进程将接收该对象作为传递给在 'message' 事件上注册的回调函数的第二个参数。套接字中接收和缓冲的任何数据都不会发送给子级。Windows 不支持发送 IPC 套接字。

¥The optional sendHandle argument that may be passed to subprocess.send() is for passing a TCP server or socket object to the child process. The child process will receive the object as the second argument passed to the callback function registered on the 'message' event. Any data that is received and buffered in the socket will not be sent to the child. Sending IPC sockets is not supported on Windows.

可选的 callback 是一个函数，在消息发送后但在子进程可能收到消息之前调用。该函数使用单个参数调用：成功时为 null，失败时为 Error 对象。

¥The optional callback is a function that is invoked after the message is sent but before the child process may have received it. The function is called with a single argument: null on success, or an Error object on failure.

如果没有提供 callback 函数，无法发送消息，ChildProcess 对象将触发 'error' 事件。例如，当子进程已经退出时，可能会发生这种情况。

¥If no callback function is provided and the message cannot be sent, an 'error' event will be emitted by the ChildProcess object. This can happen, for instance, when the child process has already exited.

如果通道已关闭或未发送消息的积压超过阈值（这使得发送更多消息是不明智的），则 subprocess.send() 将返回 false。否则，该方法返回 true。callback 函数可以用来实现流量控制。

¥subprocess.send() will return false if the channel has closed or when the backlog of unsent messages exceeds a threshold that makes it unwise to send more. Otherwise, the method returns true. The callback function can be used to implement flow control.