Oracle-Fehlermeldung „TNS: Listener kann in Connect-Deskriptor angegebenen Service aktuell nicht auflösen“ beheben

Nach einer Umstellung der Oracle-Datenbank beim Kunden, haben wir folgende Fehlermeldung in unserer ASP.NET-MVC-Webanwendung erhalten:

TNS: Listener kann in Connect-Deskriptor angegebenen Service aktuell nicht auflösen

Der Callstack („Aufrufstapel“) sah so aus:

OracleInternal.Network.NetworkException

bei OracleInternal.Network.OracleCommunication.DoConnect(String tnsDescriptor)
bei OracleInternal.ServiceObjects.OracleConnectionImpl.Connect(ConnectionString cs, Boolean bOpenEndUserSession)

Die Ursache war ein Fehler in der Verbindungszeichenfolge („Connection String“).

Statt folgendem Connection String:

DATA SOURCE=192.168.148.111:1530/SXY; User Id=MyUser; Password=MyPassword;

Haben wir diesen hier verwendet:

DATA SOURCE=192.168.148.111:1530/SXY.EXAMPLE.ORG; User Id=MyUser; Password=MyPassword;

Danach ging es.

Keine Ahnung, was da genau der Unterschied ist; entweder braucht der DNS wirklich den Full Qualified Name (was ich bezweifle, da wir ja die IP-Adresse schon angegeben hatten), oder es ist dieser Unterschied zwischen „SID“ und „Service-Name“.

Ersteres könnte die SID gewesen sein, letzteres, der Service-Name. Die neue Datenbank erwartet also immer den Service-Namen und nicht mehr die SID.

Dropbox error „Can’t establish secure internet connection“

Problem

Starting yesterday in our corporate office (all sharing the same internet connection) we found two PCs suddenly are not syncing with Dropbox anymore, showing the well known „Can’t establish secure internet connection“ error.

Other PCs work normally.

We are located in Germany and using Windows 8.1 PCs. All Dropbox clients are up-to-date (version 3.2.4).

Upon further investigation and using Process Monitor from SysInternals I found that the erronous PCs create connections to CloudFront servers while the working ones don’t.
An example would be

server-54-230-198-253.lhr50.r.cloudfront.net

When entering the URL https://server-54-230-198-253.lhr50.r.cloudfront.net into my browser, I get an error

ERR_SSL_VERSION_OR_CIPHER_MISMATCH

While I don’t know whether my investigation is actually related to the error, I still want to report it here.

When entering the mentioned server into an online SSL validator, it says:

No SSL certificates were found on server-54-230-198-253.lhr50.r.cloudfront.net. Make sure that the name resolves to the correct server and that the SSL port (default is 443) is open on your server’s firewall.

Solution

The solution was actually simple, once we figured out:

  1. Log the client off from Dropbox
  2. Log in as another Dropbox user
  3. Log that other Dropbox user off again from the client
  4. Log in the original Dropbox user which failed initially

Now the sync works again. Verified for two PCs. Also the erroneous server-54-230-198-253.lhr50.r.cloudfront.net URL is not contacted anymore.

The Dropbox support was just as you would expect: Sending late, unhelpful robot texts, claiming I was too stupid to read the documentation or have a working firewall.

So still great product, although aweful support.

(Cross-posted from the Dropbox „support“ forums)