'message' 事件

• message <Object> | <boolean> | <number> | <string> | <null> 发送的消息。
• sendHandle <net.Server> | <net.Socket>

如果 Node.js 进程是使用 IPC 通道衍生的（详见子进程和集群文档），则当子进程接收到父进程使用 childprocess.send() 发送的消息时触发。

消息会进行序列化和解析，收到的消息可能与发送的不完全一样。

• message <Object> | <boolean> | <number> | <string> | <null> a parsed JSON object or a serializable primitive value.
• sendHandle <net.Server> | <net.Socket> a net.Server or net.Socket object, or undefined.

If the Node.js process is spawned with an IPC channel (see the Child Process and Cluster documentation), the 'message' event is emitted whenever a message sent by a parent process using childprocess.send() is received by the child process.

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