父子进程使用管道通信，对于spawn方式创建的子进程，没有默认管道，所以需要使用此中方式，另外，通过nodejs创建出来的其他进程，比如java，c，都可以使用输入输出流来实现更复杂更安全的通信(The father child process uses pipeline communication, and there is no default pipe for the subprocesses created by the spawn mode, so we need to use this method, and other processes that are created by nodejs, such as Java, C, can use the input and output streams to achieve more complex and secure communications.)