Wireshark : Wireshark is the world's foremost network protocol analyzer. It lets you see what's happening on your network at a microscopic level. It is the de fac...
HttpWatch : An HTTP Viewer and HTTP Sniffer for IE and Firefox
Testcontainers : Testcontainers is an open source library for providing throwaway, lightweight instances of databases, message brokers, web browsers, or just about any...
Postman : Save requests and organize your APIs into Collections. Create and send any HTTP request using the awesome Postman request builder. Write your own test...
Vaurien is basically a Chaos Monkey for your TCP connections. Vaurien acts as a proxy between your application and any backend.
You can use it in your functional tests or even on a real deployment through the command-line.