A master server is VERY DIFFERENT than a standard LMP Server!
LMP uses a system called "Nat punchtrough" in order to connect clients and servers. This system allows people to host LMP games and become a server without having to open specific ports in their routers. Basically the standard LMP servers anounce themselves to a master server in a minimum interval of 5 seconds and clients ask that master server what LMP servers are available (you can configure the max requests per millisecond, default is 500). Once a client choose a LMP server, the master server introduce each other so they are connected. After they are introduced the master server leaves and data flows directly between client and the LMP server The master server needs to have an open port (default is 8700 UDP) as otherwise it would not be possible to query or register servers against it. This file in the repo hold a list of all the master servers currently available. It would be nice to have at least 5 servers as it will allow full-time support in case a master server is down, but to do that we need people that can have a computer turned on 24h and with an specific port open. If you are willing to contribute as a master server please let me know either by opening an issue o by a push request to that file so I can list you and the clients can query your computer. Also, a master server can respond to GET requests on a given TCP port (default is 8701 TCP) so you can list the servers in a website. You can specify how many GET requests you accept per millisecond in the flood control parameter (500 by default)