Tsung – Open-source multi-protocol distributed load testing tool

“The purpose of Tsung is to simulate users in order to test the
scalability and performance of IP based client/server applications.
You can use it to do load and stress testing of your servers. Many
protocols have been implemented and tested, and it can be easily
extended.It can be distributed on several client machines and is
able to simulate hundreds of thousands of virtual users
concurrently (or even millions if you have enough hardware
…).

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