mongodb sharding issue with 2.5.5 development version

Question

I am trying to perform performance testing for one of my application using MongoDB. I am using 2.5.5 development version. Sharding works fine when I try to read and write data using mongos.

To perform performance testing I need to start 600-700 mongoconnection threads to the mongos. Each thread queries around 2000 documents which is distributed on two shards. This test runs fine for few minutes but after sometime it stops working with the error "Connection refused by one of the shard". Looking closely at it I found that server runs out of ports when these many threads request data.

Could anyone please have a look and let me know if it is a MongoDB bug in the dev version or is it something which I am doing wrong while connecting to database.

your help will be much appreciated.

Thanks, Vibhu