Modem model [Technicolor TD5336]
According to information from the Ubiquiti Networks forum the port is 9339.
URL: game.clashroyaleapp.com https://gaming.stackexchange.com/questions/265516/what-are-the-ip-adresses-of-the-clash-royale-servers
Some screens of the modem settings management interface can be seen here:
[Edit]:
Configuration tree:
SETUP
Internet Setup
3G Setup
Ethernet WAN
Wireless Setting
Local Network
Time and Date
ADVANCED
Advanced Wireless
Multi-WAN
Advanced-LAN
IPv6 WAN
IPv6 LAN
DSL Settings
RIP Settings
NAT
Firewall
Static Route
Multicast
Dynamic DNS
DNS Route
Port Mapping
Quality of Service
UPnP
SNMP
SHARE
Samba
Share Management
Disk Management
Printer Server
MAINTENANCE
Password
User Configuration
Remote Manage
Remote Access
SysLog
Time Schedule
Firmware Upgrade
Backup/Restore
Ping
Diagnostic
Reboot Device
STATUS
Summary
IPv6 Info
xDSL Info
Wireless Clients
LAN Clients
Logs
Routing Table
Driver Version
Statistics
Best Answer
The firewalls on consumer routers are not that great - especially on ISP supplied systems like this one.
The "best" way to block this is at the DNS server - something like opendns would be an easy way to do it, but it looks like your router dosen't support it.
While its a bit of work, the 'right' way to do this feels like using the firewall.
Lets start by identifying the IP addresses that resolve to
game.clashroyaleapp.com
On windows, the command is nslookup. On everything else that's dig
Now we need to block these. It makes sense to block these rather than the ports since the application seems to use a large range of ports.
Essentially you need to create one rule per IP address (and periodically update it as they add servers). Unfortunately, without the router on hand, I can only guess that essentially, you need to create rules with these addresses as the source address with the interface being set to any. You'd want to set action as deny.
Of course, test this, and adjust as needed.