A Protocol Analyzer, also known as a Packet Sniffer, will record a packet and save it to your computer so you can analyze network traffic at a later time.
Wikipedia
A protocol analyzer is a tool (hardware or software) used to capture and analyze signals and data traffic over a communication channel. Such a channel varies from a local computer bus to a satellite link, that provides a means of communication using a standard communication protocol (networked or point-to-point). Each type of communication protocol has a different tool to collect and analyze signals and data.
Specific types of protocol analyzers include:
A telecom network protocol analyzer
A …