MQTT Load Simulator
There are various MQTT stress testers out there, but I find them a bit lacking. For one, it’s really hard to see when it’s the stress tester that is being overloaded, or the server. MqttLoadSimulator aims to allow better control of traffic generated and show it’s own performance:
Being written in Qt it’s not as fast FlashMQ, but it’s multi-threaded, so it will scale.
It’s open source, but you can also download a binary here. It’s provided as-is; your mileage may vary.