L'API Web ASP.NET Core su Ubuntu 14.04 LTS non ottiene la connessione SQL al server MSSQL 2008

Ho creato una piccola API web ASP.NET utilizzando MVC e Entity Framework. Sono riuscito a costruirlo e pubblicarlo per / su Ubuntu.

Quando inserisco l'url swagger si presenta come previsto. Ma quando provo ad accedere a una risorsa (fare clic su un collegamento alla web api) genera un'eccezione nei file di log che indica che non può accedere al database.

System.Data.SqlClient.SqlException: 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: 35 - An internal exception was caught) ---> System.AggregateException: One or more errors occurred. (No such device or address) ---> System.Net.Internals.SocketExceptionFactory+ExtendedSocketException: No such device or address
   at System.Net.Dns.HostResolutionEndHelper(IAsyncResult asyncResult)
   at System.Net.Dns.EndGetHostAddresses(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.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Data.SqlClient.SNI.SNITCPHandle.d__22.MoveNext()
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
   at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
   at System.Threading.Tasks.Task.Wait(TimeSpan timeout)
   at System.Data.SqlClient.SNI.SNITCPHandle..ctor(String serverName, Int32 port, Int64 timerExpire, Object callbackObject, Boolean parallel)
   --- End of inner exception stack trace ---
   at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, Boolean applyTransientFaultHandling)
   at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
   at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.Open()
   at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.Open()
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryingEnumerable.Enumerator.MoveNext()
   at Microsoft.EntityFrameworkCore.Query.QueryMethodProvider.d__3`1.MoveNext()
   at Microsoft.EntityFrameworkCore.Query.Internal.LinqOperatorProvider.d__15`2.MoveNext()
   at Microsoft.EntityFrameworkCore.Query.Internal.LinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.MoveNext()
   at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeList(JsonWriter writer, IEnumerable values, JsonArrayContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value, Type objectType)
   at Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value, Type objectType)
   at Microsoft.AspNetCore.Mvc.Formatters.JsonOutputFormatter.WriteObject(TextWriter writer, Object value)
   at Microsoft.AspNetCore.Mvc.Formatters.JsonOutputFormatter.d__9.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.d__32.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.d__31.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.d__29.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.d__23.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.d__18.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Builder.RouterMiddleware.d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.ApplicationInsights.AspNetCore.ExceptionTrackingMiddleware.d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.ApplicationInsights.AspNetCore.RequestTrackingMiddleware.d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Hosting.Internal.RequestServicesContainerMiddleware.d__3.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Http.Frame`1.d__2.MoveNext()

Bene, il database è su una macchina diversa. È pingable, risponde da un'altra macchina e anche con lo strumento Commandline è possibile interrogare il database dalla linea di comando di Linux.

La stringa di connessione è la stessa dell'indirizzo IP definut della macchina Windows, il nome del server, l'ID utente e la password.

Ci sono delle dipendenze che devono essere installate o c'è bisogno di alcune modifiche di configurazione (non ben documentate) che mi mancano?

Ci sono già un paio di domande e risposte, ma nessuna risposta è stata in grado di risolvere il problema per me.

Cose che ho provato finora:

• controlla se i file di configurazione sono copiati sul server -> sono
• stringa di collegamento hardcode -> funziona da Win7 ma non su Ubuntu
• aggiunta della porta esplicita alla stringa di connessione -> nessuna modifica
• aggiungendo il punto e virgola alla fine della stringa di connessione -> nessuna modifica
• controllare se TCP / IP e named pipe sono abilitati su SQL Server -> sono
• eseguire il ping del server dalla macchina Ubuntu -> SQL server è pingable
• testarlo con la versione di debug e release -> stesso errore
• aggiorna tutti i Nuget alle versioni neweset -> nessun cambiamento
• aggiungendo System.Data.SqlClient a project.json -> nessun cambiamento
• usa TSQL dalla shell di Ubuntu per testare il server -> usando TSQL funziona
• per curiosità ho seguito quella guida e l'ho fatta funzionare -> ancora lo stesso errore

Aggiornare:

Non c'è molta configurazione. Il codice è semplice in Startup.cs

    public void ConfigureServices(IServiceCollection services) {
        services.AddDbContext(options => options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
        //configs of other parts
    }

in appsettings.json

    "ConnectionStrings": {
        "DefaultConnection": "Server=xxx.xxx.xxx.xxx;Database=DatabaseName;user id=*****;password=*****"
    },

Ho cancellato l'indirizzo IP, ho dato un altro nome db e inserito alcune stelle per l'id utente e passwort.

Tuttavia funziona sulla mia macchina win7-x64 così com'è.