Intermittent MongoDB Connection Issue: An attempt was made to access a socket in a way forbidden by its access permissions - mongodb

Question

I get the following exception thrown occasionally when trying to write documents to my collection.
I am using MongoDB 3.0.7 hosted in mLabs. Our application is hosted in Azure (as a Web App) and I am using the C# 2.2.3 SDK.
MongoDB.Driver.MongoConnectionException: An exception occurred while
opening a connection to the server. --->
System.Net.Sockets.SocketException: An attempt was made to access a
socket in a way forbidden by its access permissions
191.235.xxx.xxx:54128 at System.Net.Sockets.Socket.Connect(IPAddress[] addresses, Int32 port)
at System.Net.Sockets.Socket.Connect(String host, Int32 port) at
MongoDB.Driver.Core.Connections.TcpStreamFactory.Connect(Socket
socket, EndPoint endPoint, CancellationToken cancellationToken) at
MongoDB.Driver.Core.Connections.TcpStreamFactory.CreateStream(EndPoint
endPoint, CancellationToken cancellationToken) at
MongoDB.Driver.Core.Connections.BinaryConnection.OpenHelper(CancellationToken
cancellationToken) --- End of inner exception stack trace --- at
MongoDB.Driver.Core.Connections.BinaryConnection.OpenHelper(CancellationToken
cancellationToken) at
MongoDB.Driver.Core.Connections.BinaryConnection.Open(CancellationToken
cancellationToken) at
MongoDB.Driver.Core.ConnectionPools.ExclusiveConnectionPool.AcquiredConnection.Open(CancellationToken
cancellationToken) at
MongoDB.Driver.Core.Servers.ClusterableServer.GetChannel(CancellationToken
cancellationToken) at
MongoDB.Driver.Core.Bindings.ServerChannelSource.GetChannel(CancellationToken
cancellationToken) at
MongoDB.Driver.Core.Bindings.ChannelSourceHandle.GetChannel(CancellationToken
cancellationToken) at
MongoDB.Driver.Core.Operations.BulkMixedWriteOperation.Execute(IWriteBinding
binding, CancellationToken cancellationToken) at
MongoDB.Driver.OperationExecutor.ExecuteWriteOperation[TResult](IWriteBinding
binding, IWriteOperation'1 operation, CancellationToken
cancellationToken) at
MongoDB.Driver.MongoCollectionImpl'1.ExecuteWriteOperation[TResult](IWriteOperation`1
operation, CancellationToken cancellationToken) at
MongoDB.Driver.MongoCollectionImpl'1.BulkWrite(IEnumerable'1 requests,
BulkWriteOptions options, CancellationToken cancellationToken) at
MongoDB.Driver.MongoCollectionBase'1.InsertOne(TDocument document,
InsertOneOptions options, CancellationToken cancellationToken)

Answer 1

This happens if you hit the sandbox limits. More details in my old answer Intermittent crashes in Azure Web Application
To know about sandbox limits please refer to https://github.com/projectkudu/kudu/wiki/Azure-Web-App-sandbox
Also came across http://www.freekpaans.nl/2015/08/starving-outgoing-connections-on-windows-azure-web-sites/ which was nicely written on the same subject
Edit - February 2018
If you are running in to this issue now, go to Diagnose and Solve Blade for your App in the Azure portal and check the TCP Connections tile. It should give you information about the site consuming the maximum ports and allow you to monitor the state connections instance wide.