A short overview of free software for Wireless sensor networks

mainly focused on researching wireless sensor networks.
This is not an extensive list.
If you can add more tools, please let us know with this form.

OMNeT++
OMNeT++ is an extensible, modular, component-based C++ simulation library and framework, primarily for building network simulators. “Network” is meant in a broader sense that includes wired and wireless communication networks, on-chip networks, queueing networks, and so on. Domain-specific functionality such as support for sensor networks, wireless ad-hoc networks, Internet protocols, performance modeling, photonic networks, etc., is provided by model frameworks, developed as independent projects. OMNeT++ offers an Eclipse-based IDE, a graphical runtime environment, and a host of other tools. There are extensions for real-time simulation, network emulation, alternative programming languages (Java, C#), database integration, SystemC integration, and several other functions.

visit the site.

ns-3
ns-3 is a discrete-event network simulator for Internet systems, targeted primarily for research and educational use. ns-3 is free software, licensed under the GNU GPLv2 license, and is publicly available for research, development, and use.

visit the site.

ShoX
ShoX is a sophisticated and scalable discrete-event ad hoc network simulator written in Java. It is geared towards mobile wireless networks with many nodes in both indoor and outdoor scenarios. As opposed to other general-purpose simulators like Opnet, OMNeT++, ns-2, etc., which all require a tremendous learning and training effort before first results can be obtained, ShoX is very straightforward to use and makes common simulation scenarios in network design like hundreds of nodes with a specific mobility generating certain traffic patterns very easy to implement. It provides an extremely flexible and clearly designed architecture where development of new models and protocols is as easy as subclassing and extending existing superclasses, which gives an immediate guidance as to the interface which is required by the simulation kernel. ShoX has strong GUI support and nodes, movements, message routing, etc. can be easily visualized. It also offers collection of statistical data and automatic generation of graphical representations (graphs).

Visit the site.