Create SDE-file returns warning but creates the file

Question

When I create an SDE-file using arcpy I get the following warning:

WARNING 000565: Could not connect to server.

This is the appropriate code

temp = r'C:\Users\admin\AppData\Local\Temp'
host = "myServer"
sdeFileName = "mySdeFile.sde"
service = "sde:oracle11g:myHost/myInstance:" + user
arcpy.CreateArcSDEConnectionFile_management(temp, sdeFileName, myHost, service, username = user, password = password, version = version)

However the file itself was created successfully and I can even put it into ArcCatalogs sde-connections-folder and open it in ArcCatalog. Thus I doubt the error occurs because of any missing privileges.

As this message is quite generic and can be caused by many different problems I don´t want to swallow it.

Has anyone a solution or at least an explanation for this?

I am using ArcGIS 10.2 and Python 2.7 for 32bit.

EDIT: When I use

arcpy.CreateDatabaseConnection_management(temp, sdeFileName, "ORACLE", service, username = user, password = password, version = version)

instead it works without any problems.
However as I also have some customers that still use Application-Server-connections I cannot use this function as there´s no information on the actual host given within the service-paramater as opposed to the DirectConnect-syntax, where the paramater includes both the host and the database-instance.

So what I need is a function that works with all the following inputs:

1. Application-Server-connection (deprecated)

   host = "myServer"
service = "5151:mySdeInstance"

2. Direct-Connect-connection

   service = "sde:oracle11g:tnsName:user"
   where tnsName corresponds the name for that connection within tnsnames.ora.

3. Easy-Connect-connection

   service = "sde:oracle11g:myServer/user:user"

Answer 1

Direct connections and 3-tier connections with geoprocessing tools must be created with separate tools. To supply a port or service name, try using the Create ArcSDE Connection File tool.

http://desktop.arcgis.com/en/arcmap/10.3/tools/data-management-toolbox/create-arcsde-connection-file.htm

arcpy.CreateArcSDEConnectionFile_management(r'c:\connectionFiles',
                                        'gpserver',
                                        '5151',
                                        '',
                                        'toolbox',
                                        'toolbox',
                                        'SAVE_USERNAME',
                                        'SDE.DEFAULT',
                                        'SAVE_VERSION')

For a direct connection, use CreateDatabaseConnection_management as suggested above.