[Perf issue] SocketException when disconnecting the SshClient

[raffaeler]

System Information:

• Library version: <PackageReference Include="SSH.NET" Version="2024.2.0" />
• .NET 9.0
• Running on Windows 10 x64

Problem:

When I invoke the Disconnect method, a SocketException is thrown.
The problem is that I have to call this code in multiple iterations and I need to re-create the connection every time. The exception is a perf hit.

Repro code:

The repro code is very simple. I tried both Connect and ConnectAsync with no differences.
As soon as I try to either Disconnect or Dispose (which calls Disconnect), the Exception is thrown.

_client = new SshClient(connectionInfo);
_client.Connect();      // //await _client.ConnectAsync(default);
_client.Disconnect();    // Exception explodes here
_client.Dispose();

System.Net.Sockets.SocketException: 'A blocking operation was interrupted by a call to WSACancelBlockingCall.'

[wa926talent]

We've encountered the same problem.

[wa926talent]

The 2025.0.0 version also has the same issue

[Rob-Hague]

I would be pretty surprised if exception handling had measurable impact compared to, for example, network communication.

Has anybody measured this, or are you just pointing out that an exception occurs?

P.S. the Socket.Poll is unnecessary here, but removing it will just move the exception into the Receive call when the socket is shut down in Disconnect.

[raffaeler]

Hi @Rob-Hague, I noticed (but not benchmarked) it because in my case I have to validate that all the configured devices can be reached successfully. Basically I have to connect and disconnect immediately as fast as possible.
The other problem is that I am using telemetry (Event Source) to monitor problems and get a huge list of these exceptions.

FYI I remember a thread in the ASP.NET Core repo where they discussing the perf gain after removing the exceptions on disconnect.