How to set a mongodb node to return as the primary of a replication set?
Typically, you don't. Thinking of your nodes in terms of primary or secondary is the wrong way to approach it. Since standard data bearing nodes should have the same dimensions, it is better to think of them as replica set members, one of which gets elected to primary. Since the drivers are replica set aware and know which the current primary is and you are supposed to give more than one server in your connection string like

mongodb://jpb01275:37001,jpb01275:37002/?replicaSet=Krishna


there is no advantage in setting a fixed replica set primary.

If you really have to do it, you need to do an 

rs.stepDown(90,30)


on the current primary and repeat that until your chosen node becomes primary, within 90 seconds (the first numeric value set). For details, see the documentation of rs.stepDown().