MongoDB: Server sockets closed after a few minutes

I am working with multiple AWS intances connected to the same MongoDB database (inside Compose.io Elastic deployment). But i am getting the error server : sockets closed after a few minutes. Can anyone give me any hint about what may be wrong with the connection code? **CONNECTION CODE** var url = "mongodb://:@:,:/?replicaSet="; var options = { server : {"socketOptions.keepAlive": 1}, replSet : { "replicaSet": , "socketOptions.keepAlive": 1 } }; MongoClient.connect(url, options, function(err, db) { ... }); **ERROR MESSAGE** Potentially unhandled rejection MongoError: server : sockets closed at null. (/var/app/current/node_modules/mongodb/node_modules/mongodb-core/lib/topologies/server.js:328:47) at g (events.js:199:16) at emit (events.js:110:17) at null. (/var/app/current/node_modules/mongodb/node_modules/mongodb-core/lib/connection/pool.js:101:12) at g (events.js:199:16) at emit (events.js:110:17) at Socket. (/var/app/current/node_modules/mongodb/node_modules/mongodb-core/lib/connection/connection.js:142:12) at Socket.g (events.js:199:16) at Socket.emit (events.js:107:17) at TCP.close (net.js:485:12)