Cannot import json files with the mongoimport included in 3.1.7. However those same file import with the exact same command using 3.1.6.

$ mongoimport version: 3.1.7
git version: not-built-with-ldflags
$ mongoimport --file grades.json
2015-08-31T14:54:12.987-0600 no collection specified
2015-08-31T14:54:12.987-0600 using filename 'grades' as collection
2015-08-31T14:54:15.988-0600 [........................] test.grades 0.0 B/93.2 KB (0.0%)
2015-08-31T14:54:16.492-0600 [........................] test.grades 0.0 B/93.2 KB (0.0%)
2015-08-31T14:54:16.492-0600 Failed: error connecting to db server: no reachable servers
2015-08-31T14:54:16.492-0600 imported 0 documents

$ mongoimport version: 3.1.6
git version: not-built-with-ldflags
$ mongoimport --file grades.json
2015-08-31T14:54:45.584-0600 no collection specified
2015-08-31T14:54:45.584-0600 using filename 'grades' as collection
2015-08-31T14:54:45.588-0600 connected to: localhost
2015-08-31T14:54:45.764-0600 imported 800 documents

Explicitly specifying the server and port does not fix the issue.