write data into Ramdisk for visualization

gRPC code will take a look at the data for visualization.

For now, it just checks the latest packets in the data file.
However, we only write a chunk of packets into data file when a input block is full.
It means we only can take a look at a packet every 16k packets.

We may need to write a few packets into Ramdisk, and then the gRPC code gets the data there for visualization. 