you can't switch between server's, you can only switch between channels for one server.
example:
main Server (127.0.0.1 7880) - here is the login
├── Channel 1 IP-127.0.0.1 Port-300 game server
└── Channel 2 IP-127.0.0.1 Port-301 game server
second server (192.168.65.65) login
├── Channel 1 IP-192.168.65.65 Port-302 game server
└── Channel 2 IP-192.168.65.65 Port-303 game server
and you need have up and running two dekaronserver.exe to have 2 channel on the same server (they can be configured different with different rate)
any way to make two server (not channel) you need configure properly server group in some config file on server side and client as well. (they must be same) And for male login for two different server you will need make own server select)
here is some guy who make this long time ago