help,I want to know about use master server.

1.what is different of master server and unity networking api(not have master server,use public ip to connect) ?
2.benefit of master server ?
3.I want to see example of master server.
4.I don't understand why we have to use the master server,when have unity networking api (use public ip to connect).

- unity networking api(not have master server)
If have initialize server public ip will save on database server ,on client open scene lobby client will see room(server1,server2,load form database) > join > play game .

- have master server
It same unity networking api,but don't use database server to save public ip.
I can create one room(server),if other create new room(server,room2 or first),can't create new room.

Thank you,I will wait for the answer for everyone.

 

Let's start with an example:
Player A is on the same LAN as player B. Player A starts a server instance and player B can connect to it using player A's ip address. No master server is needed because they know eachother ip address to connect directly on the same LAN.
Example 2:
Player A starts a server in his LAN at home.
Player B is connected to the internet at his home but doesn't know the ip address of player A.
When player A starts the server instance, it will send it's public ip address to the master server.
When player B wants to connect to player A, it will retrieve the ip address of player A from the master server and the master server (using the NAT facilitator) will provide NAT punchthrough if needed to make that connection possible.

 

thank you.
I found one problem(use master server).
If have player A starts the server instance and player B starts the server instance,player C can connect to server player A but player D can't connect to server B.
A(server) < C(connect to A) // can connect
B(server) < D(connect to B)// can't connect
E(server) < F(connect to B)// can't connect
G(server) < H(connect to B)// can't connect

 

But why can't they connect?
Did you debug the connection? Is the OnFailedToConnect called?
What is the error?