android 请问这种系统指令是什么指令，如何调用它，和接收返回结果

发送

void Send(String file, String cmd){
    RandomAccessFile localRandomAccessFile = new RandomAccessFile(file, "rw");
    localRandomAccessFile.writeBytes(cmd + "\r\n");
    localRandomAccessFile.close();
}

接收

void Receive(String file){
    RandomAccessFile localRandomAccessFile = new RandomAccessFile(file, "r");
    byte[] arrayOfByte = new byte[1024];
    int readSize = 0;
    while ((readSize = localRandomAccessFile.read(arrayOfByte)) == -1){

    }
    String response = new String(arrayOfByte).substring(0, readSize);
}