En la configuración NAT del router, comprueba si está configurado de este modo:
Global: Same as IP address
Internal: 192.168.1.47
Type: TCP/UDP
Start-End: 9987
Start-End: 9987
Global: Same as IP address
Internal: 192.168.1.47
Type: TCP/UDP
Start-End: 9987
Start-End: 9987