Jacky, there are different ports for different services.
50070 is HDFS service which every Hadoop system has (therefore I suggested it).
8888 is likely just a hortonworks' port for some specific web service.
50030 is Jobtracker port
First of all, make sure that you can connect/communicate with your VirtualBox (host os can access guest services). If so, find out what service/port you need e.g. Jobtracker API error - Call to localhost/127.0.0.1:50030 failed on local exception: java.io.EOFException
It can be a lot of work - so if you know Cloudera distribution has all things you need - go for Cloudera