1# Virtual Hub 2 3The idea of virtual-hub is to setup a 802.15.4 network for multiple 4QEMU nodes running zephyr application. It receive packets from QEMU 5pipes and redirect them to other QEMUs simulating a physical 6environment. 7 8This component has a similar idea of running zephyr applications with 9`make server` and `make client` which connects both virtual machines 10with a simbolic link. Here we try to expand this concept to how many 11virtual nodes do you want. 12 13The virtual-hub is a basic cmake application. To build it, follow 14the steps: 15``` 16mkdir build && cd build 17cmake .. 18make 19``` 20 21To run the virtual-hub you will need to pass an csv file 22as an argument: 23``` 24./hub ../input.csv 25``` 26 27The csv file represents a graph (conection matrix). It enables the 28possibility to simulate different topologies between the QEMU nodes. 29There is an example file in virtual-hub's directory for 3 nodes full 30connected. 31 32When building the matrix you can simulate packet drop rate: 33- 0 means that no packets will be delivered 34- 1 means that all packets will be delivered 35- If you set 0.7 means 70% of packets will be delivered 36 37When building the zephyr application it is necessary to enable the 38QEMU pipes management mechanism. To do this we must set QEMU_PIPE_STACK 39to 1 on CMakeLists.txt from the target projects. 40 41Finally, We need to setup the pipe id using `QEMU_PIPE_ID` to reference 42the pipe which will be used by the QEMU instance. Basically, this 43operation mode will create a different linux pipe for each QEMU 44based on `QEMU_PIPE_ID`. 45 46To make this, we can use cmake parameters: 47``` 48cd zephyr-application 49mkdir build-1 && cd build-1 50cmake -DQEMU_PIPE_ID=1 .. 51make 52make node 53``` 54 55The `QEMU_PIPE_ID` defined for each zephyr-application represents a line in 56the connection matrix from `input.csv`. This way the first line and column 57from the file refers to the node with `QEMU_PIPE_ID` defined with 1. In the 58same way the second line and column from the file refers to the node with 59`QEMU_PIPE_ID` 2, and so on. 60 61The `make node` command assure the node will setup the pipe correctly. 62Remember to run all the QEMU nodes you want to be present in the network 63before starting the virtual-hub. 64
