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I cannot connect to RDS SQL Server 2014 Express instance from EC2 Windows 2012 server instance.

1. I cannot connect through UDL file, and also not through my asp.net mvc web application.

Windows EC2 Instnace ID: i-0fe6390a77605e7f2
Availaibility Zone: us-east-2c

RDS SQL Server Instnace ID: tandt-201901-2
RDS SQL Server Zone: us-east-2c

I am able to connect to this RDS SQL Server through following on port 1433 :
1. SQL Server Management Studio from my development laptop
2. UDL File from my development laptop
3. Asp.NET MVC 4 Entity framework Web App from my development laptop.

Detailed Error Message from asp.net mvc web application is pasted below:

[Win32Exception (0x80004005): The wait operation timed out]

[SqlException (0x80131904): A network-related or instance-specific
error occurred while establishing a connection to SQL Server. The
server was not found or was not accessible. Verify that the instance
name is correct and that SQL Server is configured to allow remote
connections. (provider: TCP Provider, error: 0 - The wait operation
timed out.)]

System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection
owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean
allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions
userOptions, DbConnectionInternal& connection) +345

System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection
owningObject, TaskCompletionSource1 retry, DbConnectionOptions
userOptions, DbConnectionInternal& connection) +156

System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection
owningConnection, TaskCompletionSource1 retry, DbConnectionOptions
userOptions, DbConnectionInternal oldConnection, DbConnectionInternal&
connection) +258

System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection
outerConnection, DbConnectionFactory connectionFactory,
TaskCompletionSource1 retry, DbConnectionOptions userOptions) +312

System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource1
retry) +202

System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource1
retry) +413 System.Data.SqlClient.SqlConnection.Open() +128

System.Data.EntityClient.EntityConnection.OpenStoreConnectionIf(Boolean
openCondition, DbConnection storeConnectionToOpen, DbConnection
originalConnection, String exceptionCode, String attemptedOperation,
Boolean& closeStoreConnectionOnFailure) +40 [EntityException: The
underlying provider failed on Open.]

System.Data.EntityClient.EntityConnection.OpenStoreConnectionIf(Boolean
openCondition, DbConnection storeConnectionToOpen, DbConnection
originalConnection, String exceptionCode, String attemptedOperation,
Boolean& closeStoreConnectionOnFailure) +208

System.Data.EntityClient.EntityConnection.Open() +128

System.Data.Objects.ObjectContext.EnsureConnection() +83

System.Data.Objects.ObjectQuery1.GetResults(Nullable1
forMergeOption) +48

System.Data.Objects.ObjectQuery1.System.Collections.Generic.IEnumerable.GetEnumerator()
+40 System.Linq.Enumerable.First(IEnumerable`1 source) +212

Your urgent help is required to solve this issue.