Manish,
That should n't be the case.
If you are able to do the device registration from Rest Client successfully with 8080, then atleast the http(s)://SMP_Server_IP_Address:8080 should be accessible from SMP server browser, which is n't your case.
Did you find any logs in SMP server (or) the logs at the mobile device by using ADB or Xcode tools?
Can you give a try restarting SMP server ?
Regards
Virinchy