Renci.SshNet.Sftp iOS iPad - Connection Error

I've a problem while connecting with a sftp - Server with my iPad iOS 14.4.1.

I'm using the Renci.SshNet.Sftp Framework. On Mac Osx or Windows everything works perfectly. But on iPad its stops working at "sshClient.Connect();" I put the private key file into the StreamingAssets Folder.

I'm using port 22. The server does not get any connection try.

Code (CSharp):

1. public void DownloadDirectory()
2.     {
3.         Renci.SshNet.ConnectionInfo conn =
4.     new ConnectionInfo(hostName, port, username, new AuthenticationMethod[]
5.         {
6.          
7.         new PrivateKeyAuthenticationMethod(username, new PrivateKeyFile[]
8.                { new PrivateKeyFile(Application.streamingAssetsPath + "/privatekeyFile", "") }),
9.         });
10.         try
11.         {
12.             using (var sshClient = new SftpClient(conn))
13.             {
14.                 sshClient.Connect();
15.                 var files = sshClient.ListDirectory(directory);
16.                 foreach (var file in files)
17.                 {
18.                     if (!file.Name.StartsWith(".") && file.Name.StartsWith(localFileName))
19.                     {
20.                         string remoteFileName = file.Name;
21.                         using (Stream file1 = File.OpenWrite(Application.streamingAssetsPath + localFileName))
22.                         {
23.                             Debug.Log(directory + remoteFileName);
24.                             sshClient.DownloadFile(directory + remoteFileName, file1);
25.                         }
26.                     }
27.                 }
28.             }
29.         }
30.         catch (Renci.SshNet.Common.SshConnectionException)
31.         {
32.             Debug.LogError("Cannot connect to the server.");
33.         }
34.         catch (System.Net.Sockets.SocketException)
35.         {
36.             Debug.LogError("Unable to establish the socket.");
37.         }
38.         catch (Renci.SshNet.Common.SshAuthenticationException)
39.         {
40.             Debug.LogError("Authentication of SSH session failed.");
41.         }
42.     }
43.  

Error Message from Xcode.

Code (CSharp):

1. (Filename: ./Runtime/Export/Debug/Debug.bindings.h Line: 35)
2.  
3.     NullReferenceException: Object reference not set to an instance of an object.
4.       at System.Linq.Expressions.Interpreter.LightLambda.MakeRunDelegateCtor (System.Type delegateType) [0x00000] in <00000000000000000000000000000000>:0
5.       at System.Linq.Expressions.Interpreter.LightLambda.GetRunDelegateCtor (System.Type delegateType) [0x00000] in <00000000000000000000000000000000>:0
6.       at System.Linq.Expressions.Interpreter.LightLambda.MakeDelegate (System.Type delegateType) [0x00000] in <00000000000000000000000000000000>:0
7.       at System.Linq.Expressions.Interpreter.LightDelegateCreator.CreateDelegate (System.Runtime.CompilerServices.IStrongBox[] closure) [0x00000] in <00000000000000000000000000000000>:0
8.       at System.Linq.Expressions.Interpreter.LightDelegateCreator.CreateDelegate () [0x00000] in <00000000000000000000000000000000>:0
9.       at System.Linq.Expressions.Expression`1[TDelegate].Compile (System.Boolean preferInterpretation) [0x00000] in <00000000000000000000000000000000>:0
10.       at System.Linq.Expressions.Expression`1[TDelegate].Compile () [0x00000] in <00000000000000000000000000000000>:0
11.       at System.Runtime.CompilerServices.CallSite`1[T].CreateCustomNoMatchDelegate (System.Reflection.MethodInfo invoke) [0x00000] in <00000000000000000000000000000000>:0
12.       at System.Runtime.CompilerServices.CallSite`1[T].MakeUpdateDelegate () [0x00000] in <00000000000000000000000000000000>:0
13.       at System.Runtime.CompilerServices.CallSite`1[T].GetUpdateDelegate (T& addr) [0x00000] in <00000000000000000000000000000000>:0
14.       at System.Runtime.CompilerServices.CallSite`1[T].GetUpdateDelegate () [0x00000] in <00000000000000000000000000000000>:0
15.       at System.Runtime.CompilerServices.CallSite`1[T]..ctor (System.Runtime.CompilerServices.CallSiteBinder binder) [0x00000] in <00000000000000000000000000000000>:0
16.       at System.Runtime.CompilerServices.CallSite`1[T].Create (System.Runtime.CompilerServices.CallSiteBinder binder) [0x00000] in <00000000000000000000000000000000>:0
17.       at Renci.SshNet.Session.HandleMessageCore (Renci.SshNet.Messages.Message message) [0x00000] in <00000000000000000000000000000000>:0
18.       at Renci.SshNet.Session.MessageListener () [0x00000] in <00000000000000000000000000000000>:0
19.       at System.Action.Invoke () [0x00000] in <00000000000000000000000000000000>:0
20.       at Renci.SshNet.Abstractions.ThreadAbstraction+<>c__DisplayClass1_0.<ExecuteThread>b__0 (System.Object o) [0x00000] in <00000000000000000000000000000000>:0
21.       at System.Threading.WaitCallback.Invoke (System.Object state) [0x00000] in <00000000000000000000000000000000>:0
22.       at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context (System.Object state) [0x00000] in <00000000000000000000000000000000>:0
23.       at System.Threading.ContextCallback.Invoke (System.Object state) [0x00000] in <00000000000000000000000000000000>:0
24.       at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, System.Boolean preserveSyncCtx) [0x00000] in <00000000000000000000000000000000>:0
25.       at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, System.Boolean preserveSyncCtx) [0x00000] in <00000000000000000000000000000000>:0
26.       at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem () [0x00000] in <00000000000000000000000000000000>:0
27.       at System.Threading.ThreadPoolWorkQueue.Dispatch () [0x00000] in <00000000000000000000000000000000>:0
28.       at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback () [0x00000] in <00000000000000000000000000000000>:0
29.  
30.     (Filename: currently not available on il2cpp Line: -1)

Hope you can help me.
Is Renci.sshnet supporting iOS devices ?

Regards

MotionBrain