Create an input stream from network source hostname:port, where data is received as serialized blocks (serialized using the Spark's serializer) that can be directly pushed into the block manager without deserializing them. This is the most efficient
way to receive data.

def rawSocketStream[T: ClassTag](hostname: String, port: Int,
      storageLevel: StorageLevel = StorageLevel.MEMORY_AND_DISK_SER_2):
    ReceiverInputDStream[T]