Do you want to build by yourself a LAN server right on your Windows computer? Here you have some steps to do it works.
#1) Go to openspeedtest.com;
#2) Click on DOWNLOAD link;
#3) Download and install;
#3.1) Make sure to check "Private networks, ..." to allow access
#4) This is the link that includes the server ip address and the default port is 3000:
On the same local network as the server, try to test the network speed - you can use any web browser to enter the server ip address.
You just need to click on Start to start testing the network speed - as you can see in the official script below: