Network sniffers in testing

Nowadays programmers tend to use third party libraries, frameworks and services rather than to write code themselves.

As a result our software executes the code written by other programmers and sometimes it can contain defects which may lead to failures that are not easy to reproduce.

What if the software provides users with access to the third party content using infrastructure that is rented, on devices which live their own life? In this circumstances, it is vitally important to know what exactly is happening. The source of this information is the data passed via network: requests, responses, streams. Everything that happens there are truth, arguments for discussion, information for analysis, samples for testing, specifics of interacting systems behaviour.

Today I would like to tell which tools exist for collecting and analysing network traffic, how and where they may be applied and I will provide some real cases which were solved using the network traffic analysis.