A timeout occured after 30000ms selecting a server using CompositeServerSelector{ Selectors = ReadPreferenceServerSelector{ ReadPreference = { Mode = Primary, TagSets = [] } }, LatencyLimitingServerSelector{ AllowedLatencyRange = 00:00:00.0150000 } }. Client view of cluster state is { ClusterId : "2", ConnectionMode : "Automatic", Type : "Unknown", State : "Disconnected", Servers : [{ ServerId: "{ ClusterId : 2, EndPoint : "Unspecified/localhost:27037" }", EndPoint: "Unspecified/localhost:27037", State: "Disconnected", Type: "Unknown", HeartbeatException: "MongoDB.Driver.MongoConnectionException: An exception occurred while opening a connection to the server. ---> System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it 127.0.0.1:27037 at System.Net.Sockets.Socket.InternalEndConnect(IAsyncResult asyncResult) at System.Net.Sockets.Socket.EndConnect(IAsyncResult asyncResult) at System.Threading.Tasks.TaskFactory`1.FromAsyncCoreLogic(IAsyncResult iar, Func`2 endFunction, Action`1 endAction, Task`1 promise, Boolean requiresSynchronization) --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at MongoDB.Driver.Core.Connections.TcpStreamFactory.<ConnectAsync>d__7.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at MongoDB.Driver.Core.Connections.TcpStreamFactory.<CreateStreamAsync>d__4.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at MongoDB.Driver.Core.Connections.BinaryConnection.<OpenHelperAsync>d__47.MoveNext() --- End of inner exception stack trace --- at MongoDB.Driver.Core.Connections.BinaryConnection.<OpenHelperAsync>d__47.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at MongoDB.Driver.Core.Servers.ClusterableServer.<HeartbeatAsync>d__42.MoveNext()" }] }.