NetworkStream read abends application

Question

NetworkStream read abends application

Brown, Matt 106

I am running into an issue where a read abends my application. Is there a way to handle it in a more soft way so I get the error data, but have it not stop my application. Is it a simply case of changing the LogError functions to a LogInfo? It is slightly odd that the write seems to work and not the read. Code and error message is below.

Code

private string SendReceive(string message, string clientAddress, int id)
{
    try
    {
        // Create a TcpClient. 
        // Note, for this client to work you need to have a TcpServer  
        // connected to the same address as specified by the server, Port 
        // combination.
        if (clientAddress.Equals("localhost"))
            clientAddress = "127.0.0.1";
        var client = new TcpClient(clientAddress, Port);
        byte[] data = Encoding.ASCII.GetBytes(message);
        NetworkStream stream = client.GetStream();
        stream.ReadTimeout = 250;
        stream.Write(data, 0, data.Length);
        Log.LogInfo("Sent for note: " + id + " with " + message);
        data = new byte[256];
        // Read the first batch of the TcpServer response bytes.
        int bytes = stream.Read(data, 0, data.Length);
        string responseData = Encoding.ASCII.GetString(data, 0, bytes);
        client.Close();
        // stream.Close(); 
        Log.LogInfo("Note: " + id + " reply from server " + responseData);
        responseData = responseData.ToUpper();
        return responseData;
    }
    catch (ObjectDisposedException e)
    {
        Log.LogError(MethodBase.GetCurrentMethod().Name, e.Message, e);
    }
    catch (ArgumentOutOfRangeException e)
    {
        Log.LogError(MethodBase.GetCurrentMethod().Name, e.Message, e);
    }
    catch (InvalidOperationException e)
    {
        Log.LogError(MethodBase.GetCurrentMethod().Name, e.Message, e);
    }
    catch (ArgumentNullException e)
    {
        Log.LogError(MethodBase.GetCurrentMethod().Name, e.Message, e);
    }
    catch (IOException e)
    {
        Log.LogError(MethodBase.GetCurrentMethod().Name, e.Message, e);
    }            
    catch (SocketException e)
    {
        Log.LogError(MethodBase.GetCurrentMethod().Name, e.Message, e);
    }
    catch (Exception ex)
    {
        Log.LogError(MethodBase.GetCurrentMethod().Name, "Exception in ESPComm.SendReceive: {0}", ex);
        Log.LogInfo("Exception returned: " + ex.Message);
    }

Error Message


3/11/2025 3:45:17 PM: Error: Unable to read data from the transport connection: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
Unable to read data from the transport connection: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
   at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
   at AppService.Util.Comm.SendReceive(String message, String clientAddress, Int32 id) in C:\services\App_Service\Utils\Comm.cs:line 52
3/11/2025 3:45:21 PM: Error: No connection could be made because the target machine actively refused it (IP Address)
No connection could be made because the target machine actively refused it (IP Address)
   at System.Net.Sockets.TcpClient..ctor(String hostname, Int32 port)
   at AppService.Util.Comm.SendReceive(String message, String clientAddress, Int32 id) in C:\services\App_Service\Utils\Comm.cs:line 44

1 answer

Your answer

Answer 1

Log.LogError isn't going to terminate your app unless it also throws an exception. You didn't post all the code in that function so it is hard to say what is going on here. It seems like your code is handling all the errors, although I don't know that this is a good idea. What you need to look at is what exception is actually causing the app to crash. If you're running in the debugger then it'll show you the actual line crashing your app.

As for your code, I think you can simplify it down quite a bit. It is unclear to me why you're handling very specific exceptions and logging them but generating a different log for everything else. If you really need this behavior then consider creating an exception filter instead. This would make it very easy to add new exceptions while keeping the code small.

try
{
   ... 
} catch (Exception error) when (IsSpecialError(e))
{
   //Log special exceptions here
} catch (Exception error)
{
   //Everything else lands here
};

private static bool IsSpecialError ( Exception error )
{
   //Nothing special...
   return false;
}

Looking at what could cause the issue I see the following things that raise some concerns:

Creating a new TcpClient each time can be wasteful. If you are talking to the same client then create the TcpClient once and reuse it. Otherwise wrap it in a using statement otherwise you are leaking a TcpClient every time your code throws an exception.
You are setting the ReadTimeout to 250ms. That is pretty fast. Interestingly the first error you log is related to the timeout of the read. Unless you have specific requirements then don't set the read timeout from its default value.
You should never handle exceptions unless you can do something about them. This, of course, excludes logging the exception and then rethrowing. In your case you're handling exceptions that should crash your app as they are true error cases. Referencing a disposed object indicates a lifetime issue. Argument exception indicates bad code, etc. Only handle exceptions that you can do something about. In all other cases log the exception and rethrow it. Maybe the caller can better handle the error. This also plays into what you're going to return if an error does occur.

Here is a first pass at how I might rewrite your code.

private string SendReceive(string message, string clientAddress, int id)
{
    // Create a TcpClient. 
    // Note, for this client to work you need to have a TcpServer  
    // connected to the same address as specified by the server, Port 
    // combination.
    if (clientAddress.Equals("localhost"))
        clientAddress = "127.0.0.1";

    byte[] data = Encoding.ASCII.GetBytes(message);
    
    try
    {
       using var client = new TcpClient(clientAddress, Port);
       NetworkStream stream = client.GetStream();

       stream.Write(data, 0, data.Length); 
       Log.LogInfo("Sent for note: " + id + " with " + message);

       data = new byte[256];
       // Read the first batch of the TcpServer response bytes.
       int bytes = stream.Read(data, 0, data.Length);
       string responseData = Encoding.ASCII.GetString(data, 0, bytes);
   
       Log.LogInfo("Note: " + id + " reply from server " + responseData);
       responseData = responseData.ToUpper();
       return responseData;
    } catch (IOException e)
    {
        Log.LogError(MethodBase.GetCurrentMethod().Name, e.Message, e);
        return "IO ERROR";
    } catch (SocketException e)
    {
        Log.LogError(MethodBase.GetCurrentMethod().Name, e.Message, e); 
        return e.Message;
    } catch (Exception ex)
    {
        Log.LogError(MethodBase.GetCurrentMethod().Name, "Exception in ESPComm.SendReceive: {0}", ex);
        Log.LogInfo("Exception returned: " + ex.Message);

        //Nothing to do here so fail
        throw;
    }

    //Will never get here...
}

I would probably go even further and refactor the read/write into separate functions if they are more complex than what is shown here.

Brown, Matt 106 Reputation points

2025-03-12T16:18:54.29+00:00

The only missing code is the return statement to return an empty string after all of the exceptions have been handled, IE "return string.Empty;"

The timeout code is there and helps produce an error message. Without it as per your code, I receive no error message.

Currently, the first LogInfo works. The second one dose not. The error message is the previously mentioned "unable to read" message which is fine. I just want the application to still run even if the read fails. Based on documentation, it should hit the IO Exception and continue to run, but it doesn't.

Log.LogInfo("Sent for note: " + id + " with " + message); data = new byte[256]; // Read the first batch of the TcpServer response bytes. int bytes = stream.Read(data, 0, data.Length); string responseData = Encoding.ASCII.GetString(data, 0, bytes); Log.LogInfo("Note: " + id + " reply from server " + responseData);
Michael Taylor 57,216 Reputation points

2025-03-12T16:42:55.7566667+00:00

I don't understand what you mean by "just want the application to still run". If an exception is raised then the catch block is executed and you get your error log, as you said you are getting. Then it'll jump out of the try-catch and go to the next line which you are saying returns an empty string. At that point this function is done. If your app is terminating then you need to look at what the caller of this method is doing with the results.

If you're running this code via the debugger you should be able to get an exception dialog if the app is crashing. The exception dialog should identify the callstack of the error. Is it inside this function? If so then what line?
Brown, Matt 106 Reputation points

2025-03-12T19:58:49.33+00:00

This is the line it points to. I did some testing before adding info and one of my test didn't stop the application. Every other test has stopped the application, and the only difference in the one which worked was a logging statement. The quirk is we updated the DB from MySQL 5.7 to 8, and suddenly this started to happen even though the DB works perfectly fine with interacting with any application which uses it including logging any message.

int bytes = stream.Read(data, 0, data.Length);

Update, I cleaned out the Test log table as there had been no trimming of that table in a decade so there was literally millions of records in it. I reran the application in Test and twice it ran without stopping. It's just weird see the record inserted and yet the application stops. I had already cleaned out the Prod database, so I had ruled out that as a solution for Test. I think it is the cleaning out of the table and the code change which makes it work.
Michael Taylor 57,216 Reputation points

2025-03-12T20:19:53.73+00:00

If the line you mentioned throws an exception then your catch block would be triggered to log it. Then execution would fall through to the first line after the catch blocks. If it times out because of your short timeout setting then it would call the catch (Exception) version because you aren't handling that exception. If the read itself failed then most likely your catch (IOException) would be triggered.

In both cases you call Log.LogError. Is this a method you wrote? If so then you'll want to ensure it doesn't throw an exception. If an exception occurs while handling an exception then the original exception is lost and the new exception triggers exception-handling again. In your case I suspect it would then crash the program. However the stack trace would point to the Log.LogError line and not the original read line.

Since we have no visibility into your database stuff I cannot explain why changing that would fix anything. The line you said is failing has nothing to do with a database. Again, if the Log call throws an exception then I'd expect it to show up in the call stack for the exception that is crashing your app. Ensure your Log calls are exception safe.

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NetworkStream read abends application

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