A packet analyzer is also known as a packet sniffer or a network protocol analyzer. Packet analyzer has the ability to grab the raw packet from the wire, wireless, Bluetooth, VLAN, PPP, and other network types, without getting processed by the application. By doing so it brings the whole science and innovation to this field. In this chapter we will see a few use cases of the packet analyzer by covering the following topics:
More practically, packet analyzers are employed in network security and to analyze raw traffic so as to detect scans and attacks, and for sniffing, network troubleshooting, and many more uses, as shown in the following image:

Packet analyzers can be used as follows:
The use is not limited to these bullet point, there are lots of new tools and innovations happening in this area. Find a use case and build your own packet analyzer; the best example is Wireshark.