WCF - Many many many first chance exceptions being thrown - then crashes App

I have a WPF application (Host) that is, among other things, self-hosting WCF with a number of ServiceHosts (an example shown below)

host= new ServiceHost(typeof(Data));
ServiceEndpoint endpoint = _HostData.AddServiceEndpoint(typeof(IData), _tcpBindingBO, _netTcpAddress + "data");


// add throttle behaviour
ServiceThrottlingBehavior throttle = host.Description.Behaviors.Find<ServiceThrottlingBehavior>();
if (throttle == null)
{
    throttle = new ServiceThrottlingBehavior();

    throttle.MaxConcurrentCalls = _SymphonyHostProp.MaxConcurrentCalls;     // 200;         // default 16       // 64
    throttle.MaxConcurrentInstances = _SymphonyHostProp.MaxConcurrentInstances; // 1000;     // default 26       // 464
    throttle.MaxConcurrentSessions = _SymphonyHostProp.MaxConcurrentCalls;      // default 10       // 400

    host.Description.Behaviors.Add(throttle);
}

// open the host - bring it into life!
host.Open();

I have clients that connect to this Host using nettcpbinding like this

int MaxBuffer = 64;     // 64 Mb
int bufferSize = MaxBuffer * 1024 * 1024;   // 67108864               

// -----------------------------------------
// binding for normal clients (default) 
// -----------------------------------------
_tcpBinding = new NetTcpBinding(SecurityMode.None, true);
_tcpBinding.MaxBufferPoolSize = bufferSize; // 64 Mb
_tcpBinding.MaxBufferSize = bufferSize;
_tcpBinding.MaxReceivedMessageSize = bufferSize;
_tcpBinding.TransferMode = TransferMode.Buffered;
_tcpBinding.ReaderQuotas.MaxArrayLength = bufferSize;
_tcpBinding.ReaderQuotas.MaxBytesPerRead = bufferSize;
_tcpBinding.ReaderQuotas.MaxStringContentLength = bufferSize;
_tcpBinding.MaxConnections = 100;
//_tcpBinding.ReceiveTimeout = new TimeSpan(0, 0, 5);
_tcpBinding.SendTimeout = MyHost.SendTimeout;
_tcpBinding.ReliableSession.Enabled = true;
//tcpBinding.ReliableSession.InactivityTimeout = new TimeSpan(7, 0, 0, 0);    // 7 days

The 'data' exposed object is defined like this:

[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall,
ConcurrencyMode = ConcurrencyMode.Multiple,
UseSynchronizationContext = false)]  
public class Data : HBase, IData

The problem is that during normal running of the host and about 50 users connected all of sudden the Output window in the IDE is showing hundreds of wcf related errors coming in.

Then if I am lucky it goes away by itself after a a few seconds but during this time the entire UI and everything of the host application freezes up and WCF is not serving any other users anymore. Then when it comes back it all is fine until it starts to go wrong again..

There don't seem to be any internal network issues here. I have had tracing enabled but I couldn't find much useful info in it. I just wonder if anyone has experienced this behaviour?

I am happy to provide much more information if need be!

1000's of these errors are created in my output window.

A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketExc开发者_如何学Ception' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll

First chance exceptions are not errors. These are usually exceptions which will be caught. You should ignore them.

The exceptions you should worry about are exceptions which are not caught.

I recently came across this issue. In my case I was using a custom log4net WCF Appender and log4net library is designed to never throw uncaught exceptions which is why I was getting the A first chance exception in the debug window. I simply had to wrap my client making the call and the service itself in try catch blocks so that I could intercept the exception before log4net did and this allowed me to find the true cause.

While your exceptions seem to stem from a different problem, the solution would still be the same. Get those try/catches up so you can get the full error details and identify the source of the issue.

Btw, if your whole application is crashing, you can use a very handy trick to get the uncaught exception which crashed it. Simply call this as soon as the application starts,

AppDomain.Current.UnhandledException += (sender, error) => File.AppendAllText("Fatal.log", error.ExceptionObject.ToString() + "\r\n");