Socket error 10056

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• A little info about what you are doing with the socket would help.  Look in the debugger stack window to find out which of your calls led to the assertion.

  Did you call a socket function from a thread that did not create the socket?

• It is not the thread issue, I think. It looks like the synchronization between server and client. The problem happens at the Receive(buff, 4096)) line at client side.

  TCHAR buff[4096];

  int nRead = 4096;

  if ((nRead = m_pClientSock->Receive(buff, 4096)) == SOCKET_ERROR)

  {

  }

  Sometimes, Receive() line can receive the feedback information from server side. But sometimes, it brings the error mentioned in my post. It does not always happen. Also, when I set the breakpoint and this line is hit, it did not assign a value
  to the nRead, and it popuped the error window immediately.

  Any ideas ? Thanks.

• The assertion indicates that the socket does not exist, or exists in a different thread. Did the socket Create call return success? Maybe the socket has been closed? Destroyed? Or m_pClientSock is not pointing at the socket?

• More information. If Receive() line runs before the server sends data back to client, it will cause the error. If Receive()
  line runs after the server sends data back to client, it works. Any ideas about how the client side knows the server sends data back? 

  I put the try … catch block for Receive()
  line to catch the error exception, but the error cannot be caught, and the error window is immediately popups.
  How to do exception handling here? 

  Thanks.

• Now I just put the 5 seconds waiting, Sleep(5000), before the  Receive() line, and no error happens. But
  it will worse the performance. Thanks.

• To know when the server sends data back the client side creates a message-only window (m_hSocketWindow in the ASSERT) to receive a Windows message posted by winsock.  The assertion failure shows that you do not have that message-only window. The window
  should be created in sockcore.cpp line 476.  You could check that, and then check all the places m_hSocketWindow is modified to try and find out why you don’t have the message-only window.

  An assertion is not an exception and cannot be caught.  An assertion is a debug tool to let the programmer know that assumed and required preconditions do not exist. It means the programmer has made a mistake, not the machine or the environment.

• What is the message-only window? How to create such message-only
  window to avoid the above error? Any examples or hyperlinks? Thanks.

• Also, after I use Sleep(5000), why will the
  message-only window be found? Any relation between the Sleep(5000) and the
  message-only window ? Thanks.

• The message-only window is created for you automatically by CSocket/CAsyncSocket.  You don’t have to do anything except create the socket normally. The window is an implementation detail that is normally of no interest. But the assertion is telling
  us that it does not exist, so it either was not created or it has been destroyed. (Or it was created in another thread.)

  There are working examples of CSocket/CAsyncSocket in MSDN, including MFCsocs here:

  http://support.microsoft.com/kb/185728/e

  You can probably find your problem by studying that sample code and comparing it to yours, by code inspection or by analyzing its operation with the debugger.

• From Visual Studio debugger, I could not find any clue for it.

  However, at the hyperlink of http://support.microsoft.com/kb/185728/e , I found out the following part:

  When you use a CSocket Receive and Send outside OnReceive and OnSend (in other words, when you use a default do-nothing OnSend and OnReceive), it is okay
  to use Receive and Send in a loop or use them with CArchive and CSocketFile.

  In fact, in my code, I am using CSocket Receive outside OnReceive. But I did not use the loop and CArchive/CSocketFile.
  Is this the reason? Any hyperlink for example for just using CSocket Receive outside OnReceive?
  Thanks.

• I would expect the window to be created before the Connect call returns, but I have not used this mode of calling outside of OnReceive and OnSend so can’t be sure. You should be able to check that with the debugger: Is the m_hSocketWindow created during
  the Connect call?

  Does your call to Connect always return non-zero? Something else to try might be waiting until you get the OnConnect callback before doing any Send or Receive calls.

• The following code is what I am using. Most of them is from the sample of http://support.microsoft.com/kb/185728/e

  When this code runs,  the line of if ( 0 == m_pClientSock->Connect(m_strServer, m_port) ) always return the code of 10056, which

  menas «The socket is not connected». If the line Sleep(8000);
  is there, it works. If this line is commented,

   it fails. 

  Perhaps, showing the code is helpful for finding the solution. Moreover, I did not see the information for

  m_hSocketWindow in the visual studio debugger. Thanks.

                  if (m_boolClient)
  		{
  			if ( m_pClientSock) 
  			{
  				if (m_pClientSock->Send((LPCTSTR)m_strSend, 
  					m_strSend.GetLength() +1) == SOCKET_ERROR)
  				{
  					wsprintf(m_szError, "Failed to send on client socket: %d", m_pClientSock->GetLastError());
  					m_pClientSock->Close();
  					delete m_pClientSock;
  					m_pClientSock = NULL;
  					AfxMessageBox (m_szError);
  					return "";
  				}
  				m_strSend = "";
  				////UpdateData(FALSE);
  			}
  			else
  			{
  				if ((m_pClientSock = new CClntSock(this)) == NULL) 
  				{
  					AfxMessageBox ("Failed to allocate client socket! Close and restart app.");
  					return "";
  				}
  								
  				
  				if (!m_pClientSock->Create())
  				{
  					wsprintf(m_szError, "Failed to create client socket: %d! Close and restart app.", m_pClientSock->GetLastError());
  					AfxMessageBox (m_szError);
  					return "";
  				}
  				
  				if (!m_pClientSock->Connect(m_strServer, m_port))
  				{
  					wsprintf(m_szError, "Failed to connect to server: %d.", m_pClientSock->GetLastError());
  					AfxMessageBox (m_szError);
  					m_pClientSock->Close();
  					delete m_pClientSock;
  					m_pClientSock = NULL;
  					return "";
  				}
  							
  				if (m_pClientSock->Send((LPCTSTR)m_strSend, m_strSend.GetLength() +1) == SOCKET_ERROR)
  				{
  					wsprintf(m_szError, "Failed to send on client socket: %d", m_pClientSock->GetLastError());
  					m_pClientSock->Close();
  					delete m_pClientSock;
  					m_pClientSock = NULL;
  					AfxMessageBox (m_szError);
  					return "";
  				}
  				
  				m_strSend = "";				
  			}
  		}
  		else
  		{
  			if ( m_pSrvrSock) 
  			{
  				m_pSrvrSock->m_sendBuffer = m_strSend;
  				m_pSrvrSock->m_nBytesSent = 0;
  				m_pSrvrSock->m_nBytesBufferSize = m_strSend.GetLength() + 1;
  				m_pSrvrSock->DoAsyncSendBuff();
  				m_strSend = "";				
  			}
  			else
  			{
  				AfxMessageBox ("Message socket not established yet");
  			}
  		}
  
  		//Sleep(8000);	
  		TCHAR buff[4096];
  		int nRead = 4096;
  
  		try
  		{			
  			if ( 0 == m_pClientSock->Connect(m_strServer, m_port) )
  			{
  				int errorNumber = m_pClientSock->GetLastError();
  				if(errorNumber != 10056) // 10056 -- "The socket is not connected"
  				{
  					wsprintf(m_szError, "Failed to Connect: %d", errorNumber);
  					m_pClientSock->Close();
  					delete m_pClientSock;
  					m_pClientSock = NULL;
  					AfxMessageBox (m_szError);
  					return "";
  				}
  			}
  
  			if ((nRead = m_pClientSock->Receive(buff, 4096)) == SOCKET_ERROR)
  			{
  				wsprintf(m_szError, "Failed to receive on client socket: %d", m_pClientSock->GetLastError());
  				m_pClientSock->Close();
  				delete m_pClientSock;
  				m_pClientSock = NULL;
  				AfxMessageBox (m_szError);
  				return "";
  			}
  		}
  		catch(CException* e)
  		{				
  			string msg = "Microscope Control failed to send receive to server: ";						
  			AfxMessageBox(msg.c_str());
  		}	
  
  		//nRead = m_pClientSock->Receive(buff, 4096); 
  
  		//if (nRead != SOCKET_ERROR)
  				
  		{
  			if (nRead)
  			{
  				buff[nRead] = 0; 
  				CString szTemp(buff);
  						
  				returnedStringFromServer = static_cast<LPCSTR>(CStringA(szTemp));
  
  				if (szTemp.CompareNoCase("bye") == 0 ) 	
  				{
  					m_pClientSock->ShutDown();
  				}
  			}
  			else 
  			{
  				m_pClientSock->Close();
  			}
  		}
  

• I have tried several times , but I haven’t got Assertion error. can you check your newwork?

• Thanks for trying. 

  I just tried it on the sample code from http://support.microsoft.com/kb/185728/e . I added the receive part after sending on the client side. Also I added the send part immediately
  after receiving on the server side. This modified sample version works. 

  At client side, when the line of 

  «if ((nRead = m_pClientSock->Receive(buff, 4096)) == SOCKET_ERROR) » runs, it waits there
  until the

  message, which is sent from server, comes back to client side.

  It looks like that the issue is the client code in our program. The client code in our program uses multiple
  

  threads. It seems that Sleep(5000) can resolve this issue, but it will worse the performance. I am looking
  

  for the different way to resolve it.
  

  Also why can Sleep(5000)
  resolve this issue in the multiple threads environment? It does not make sense for
  me, either.
  

  Any ideas about how to resolve the issue are very appreciated? Thanks a lot.

• I saw this article, and I do not know how this article can help me.

  Our client program is like this: two GUI dialogs are related with the socket. There is a main dialog when the program starts, and this main dialog call the class where the socket is located. After the the main dialog finishes, I will open another plug-in
  dialog, and this dialog also uses the class mention above. If I do not put Sleep(5000) there, the line of «ASSERT(pState->m_hSocketWindow != NULL);» in the file of sockcore.cpp (947) will run. The error window will popup. If I put the Sleep(5000) there, the
  line of «ASSERT(pState->m_hSocketWindow != NULL);» in the file of sockcore.cpp (947) will not run, at all. So no this error window popups.

  If you need more information, please let me know. Thanks.

• Also, I am wondering if I can do something before the line of «if ((nRead = m_pClientSock->Receive(buff, 4096)) == SOCKET_ERROR)», so that this line just waits until the data comes back. But I do not know what I can do for it. Now I put the Sleep(5000)
  there, which is not what I want. 

• There could be problems with «after the main dialog finishes I will open another plug-in dialog, and this dialog also uses the class mentioned above.»  When the main dialog finishes MFC starts destroying a lot of the program’s objects.  It’s hard
  to help without seeing the code.

• Thanks. How about the Sleep(5000) ? Any comments for it?

• If no socket message is waiting when you call Receive then MFC loops around in a message pump while it waits. That’s when it hits the ASSERT that the message-only window does not exist.

• Do you mean?

  If the sever side has already sent the message back to client side before Receive line runs, it does not go to pump.
  So ASSERT never hits and no error happens.

  If Receive line runs and waits there for the message back from the server side, it will loop around and hit the ASSERT.
  So the error happens. 

  This makes sense.

  So I need to figure out why the message-only window disappear. Thanks.

• I think Scott is correct.
   If the receive loop cannot get any message after sending message successfully. That will cause a Assert error.

• Thanks guys for the helps. I researched the above problem.

  On client side, the pState and pThread changed when I set a breakpoint at the line of 947 in the file of sockcore.cpp.

  I attach two images, and there are differences in pState and pThread in them. It looks like the client side multiple threads causes this issue. The upper image is the status at the whole program opens, and the lower image is the status: after the whole program
  opens, and then open the plugin.

  Could I know where I can get thus example for the client multiple threads using the CSocket/CAyncSoket? If thus example can base on the example code at http://support.microsoft.com/kb/185728/e ,
  it will be great. In fact, I would like to know how to attach/deattach the socket on the multiple threads at the client side.

  

  

• You have not made it clear whether you are creating additional threads and whether you are accessing the socket from a thread that did not create it.

  You have already been given a link that discusses what to do if that is the problem, but you replied «I do not know how this article can help me.»  Why not?

  My first response in this thread asked «Did you call a socket function from a thread that did not create the socket?» You have not answered that question. I can’t see how to help you further without a clearer description of what you are doing in your code.

• Thanks Jesse for the reply. I am still working on this problem. I tried adding AfxSocketInit in all threads, but the problem is the same. Any ideas
  about it? It will be very appreciated !

• Also I researched lots of articles/posts for this error, and the suggestion is always «attach» and «detach». But on these articles/posts, no any people say that they can finally succeed in using CSocket in their application. The example code is just from
  two articles from Microsoft, but in fact they are only a piece of short code. Can anyone provide any information so that I can find a real sample multiple threads application that uses CSocket? Thanks a lot.

  Debug Assertion Failed !

  f:ddvctoolsvc7libsshipatlmfcsrcmfcsockcore.cpp line: 947

Discover more

protected virtual bool ShouldRetryConnection (Exception ex, int attemptNumber)
{
    var sx = ex as SocketException;
    if (sx != null) {
        if (sx.ErrorCode == 10061) //connection refused
            return true;
    }
    return false;
}

var se = new SocketException((int) SocketError.ConnectionRefused);
Console.WriteLine((int)se.SocketErrorCode);
Console.WriteLine(se.ErrorCode);
Console.WriteLine(se.NativeErrorCode);

public enum SocketError
{
    SocketError = -1, // 0xFFFFFFFF
    Success = 0,
    OperationAborted = 995, // 0x000003E3
    IOPending = 997, // 0x000003E5
    Interrupted = 10004, // 0x00002714
    AccessDenied = 10013, // 0x0000271D
    Fault = 10014, // 0x0000271E
    InvalidArgument = 10022, // 0x00002726
    TooManyOpenSockets = 10024, // 0x00002728
    WouldBlock = 10035, // 0x00002733
    InProgress = 10036, // 0x00002734
    AlreadyInProgress = 10037, // 0x00002735
    NotSocket = 10038, // 0x00002736
    DestinationAddressRequired = 10039, // 0x00002737
    MessageSize = 10040, // 0x00002738
    ProtocolType = 10041, // 0x00002739
    ProtocolOption = 10042, // 0x0000273A
    ProtocolNotSupported = 10043, // 0x0000273B
    SocketNotSupported = 10044, // 0x0000273C
    OperationNotSupported = 10045, // 0x0000273D
    ProtocolFamilyNotSupported = 10046, // 0x0000273E
    AddressFamilyNotSupported = 10047, // 0x0000273F
    AddressAlreadyInUse = 10048, // 0x00002740
    AddressNotAvailable = 10049, // 0x00002741
    NetworkDown = 10050, // 0x00002742
    NetworkUnreachable = 10051, // 0x00002743
    NetworkReset = 10052, // 0x00002744
    ConnectionAborted = 10053, // 0x00002745
    ConnectionReset = 10054, // 0x00002746
    NoBufferSpaceAvailable = 10055, // 0x00002747
    IsConnected = 10056, // 0x00002748
    NotConnected = 10057, // 0x00002749
    Shutdown = 10058, // 0x0000274A
    TimedOut = 10060, // 0x0000274C
    ConnectionRefused = 10061, // 0x0000274D
    HostDown = 10064, // 0x00002750
    HostUnreachable = 10065, // 0x00002751
    ProcessLimit = 10067, // 0x00002753
    SystemNotReady = 10091, // 0x0000276B
    VersionNotSupported = 10092, // 0x0000276C
    NotInitialized = 10093, // 0x0000276D
    Disconnecting = 10101, // 0x00002775
    TypeNotFound = 10109, // 0x0000277D
    HostNotFound = 11001, // 0x00002AF9
    TryAgain = 11002, // 0x00002AFA
    NoRecovery = 11003, // 0x00002AFB
    NoData = 11004, // 0x00002AFC
}

public SocketError SocketErrorCode {
    //
    // the base class returns the HResult with this property
    // we need the Win32 Error Code, hence the override.
    //
    get {
        return (SocketError)NativeErrorCode;
    }
}

public SocketException(int errorCode) : this((SocketError)errorCode)
// ...
internal SocketException(SocketError socketError) : base(GetNativeErrorForSocketError(socketError))

private static int GetNativeErrorForSocketError(SocketError error)
{
    // SocketError values map directly to Win32 error codes
    return (int)error;
}

private static int GetNativeErrorForSocketError(SocketError error)
{
    int nativeErr = (int)error;
    if (error != SocketError.SocketError)
    {
        Interop.Error interopErr;

        // If an interop error was not found, then don't invoke Info().RawErrno as that will fail with assert.
        if (SocketErrorPal.TryGetNativeErrorForSocketError(error, out interopErr))
        {
            nativeErr = interopErr.Info().RawErrno;
        }
    }

    return nativeErr;
}

private const int NativeErrorToSocketErrorCount = 42;
private const int SocketErrorToNativeErrorCount = 40;

// No Interop.Errors are included for the following SocketErrors, as there's no good mapping:
// - SocketError.NoRecovery
// - SocketError.NotInitialized
// - SocketError.ProcessLimit
// - SocketError.SocketError
// - SocketError.SystemNotReady
// - SocketError.TypeNotFound
// - SocketError.VersionNotSupported

private static readonly Dictionary<Interop.Error, SocketError> s_nativeErrorToSocketError = new Dictionary<Interop.Error, SocketError>(NativeErrorToSocketErrorCount)
{
    { Interop.Error.EACCES, SocketError.AccessDenied },
    { Interop.Error.EADDRINUSE, SocketError.AddressAlreadyInUse },
    { Interop.Error.EADDRNOTAVAIL, SocketError.AddressNotAvailable },
    { Interop.Error.EAFNOSUPPORT, SocketError.AddressFamilyNotSupported },
    { Interop.Error.EAGAIN, SocketError.WouldBlock },
    { Interop.Error.EALREADY, SocketError.AlreadyInProgress },
    { Interop.Error.EBADF, SocketError.OperationAborted },
    { Interop.Error.ECANCELED, SocketError.OperationAborted },
    { Interop.Error.ECONNABORTED, SocketError.ConnectionAborted },
    { Interop.Error.ECONNREFUSED, SocketError.ConnectionRefused },
    { Interop.Error.ECONNRESET, SocketError.ConnectionReset },
    { Interop.Error.EDESTADDRREQ, SocketError.DestinationAddressRequired },
    { Interop.Error.EFAULT, SocketError.Fault },
    { Interop.Error.EHOSTDOWN, SocketError.HostDown },
    { Interop.Error.ENXIO, SocketError.HostNotFound }, // not perfect, but closest match available
    { Interop.Error.EHOSTUNREACH, SocketError.HostUnreachable },
    { Interop.Error.EINPROGRESS, SocketError.InProgress },
    { Interop.Error.EINTR, SocketError.Interrupted },
    { Interop.Error.EINVAL, SocketError.InvalidArgument },
    { Interop.Error.EISCONN, SocketError.IsConnected },
    { Interop.Error.EMFILE, SocketError.TooManyOpenSockets },
    { Interop.Error.EMSGSIZE, SocketError.MessageSize },
    { Interop.Error.ENETDOWN, SocketError.NetworkDown },
    { Interop.Error.ENETRESET, SocketError.NetworkReset },
    { Interop.Error.ENETUNREACH, SocketError.NetworkUnreachable },
    { Interop.Error.ENFILE, SocketError.TooManyOpenSockets },
    { Interop.Error.ENOBUFS, SocketError.NoBufferSpaceAvailable },
    { Interop.Error.ENODATA, SocketError.NoData },
    { Interop.Error.ENOENT, SocketError.AddressNotAvailable },
    { Interop.Error.ENOPROTOOPT, SocketError.ProtocolOption },
    { Interop.Error.ENOTCONN, SocketError.NotConnected },
    { Interop.Error.ENOTSOCK, SocketError.NotSocket },
    { Interop.Error.ENOTSUP, SocketError.OperationNotSupported },
    { Interop.Error.EPERM, SocketError.AccessDenied },
    { Interop.Error.EPIPE, SocketError.Shutdown },
    { Interop.Error.EPFNOSUPPORT, SocketError.ProtocolFamilyNotSupported },
    { Interop.Error.EPROTONOSUPPORT, SocketError.ProtocolNotSupported },
    { Interop.Error.EPROTOTYPE, SocketError.ProtocolType },
    { Interop.Error.ESOCKTNOSUPPORT, SocketError.SocketNotSupported },
    { Interop.Error.ESHUTDOWN, SocketError.Disconnecting },
    { Interop.Error.SUCCESS, SocketError.Success },
    { Interop.Error.ETIMEDOUT, SocketError.TimedOut },
};

private static readonly Dictionary<SocketError, Interop.Error> s_socketErrorToNativeError = new Dictionary<SocketError, Interop.Error>(SocketErrorToNativeErrorCount)
{
    // This is *mostly* an inverse mapping of s_nativeErrorToSocketError.  However, some options have multiple mappings and thus
    // can't be inverted directly.  Other options don't have a mapping from native to SocketError, but when presented with a SocketError,
    // we want to provide the closest relevant Error possible, e.g. EINPROGRESS maps to SocketError.InProgress, and vice versa, but
    // SocketError.IOPending also maps closest to EINPROGRESS.  As such, roundtripping won't necessarily provide the original value 100% of the time,
    // but it's the best we can do given the mismatch between Interop.Error and SocketError.

    { SocketError.AccessDenied, Interop.Error.EACCES}, // could also have been EPERM
    { SocketError.AddressAlreadyInUse, Interop.Error.EADDRINUSE  },
    { SocketError.AddressNotAvailable, Interop.Error.EADDRNOTAVAIL },
    { SocketError.AddressFamilyNotSupported, Interop.Error.EAFNOSUPPORT  },
    { SocketError.AlreadyInProgress, Interop.Error.EALREADY },
    { SocketError.ConnectionAborted, Interop.Error.ECONNABORTED },
    { SocketError.ConnectionRefused, Interop.Error.ECONNREFUSED },
    { SocketError.ConnectionReset, Interop.Error.ECONNRESET },
    { SocketError.DestinationAddressRequired, Interop.Error.EDESTADDRREQ },
    { SocketError.Disconnecting, Interop.Error.ESHUTDOWN },
    { SocketError.Fault, Interop.Error.EFAULT },
    { SocketError.HostDown, Interop.Error.EHOSTDOWN },
    { SocketError.HostNotFound, Interop.Error.EHOSTNOTFOUND },
    { SocketError.HostUnreachable, Interop.Error.EHOSTUNREACH },
    { SocketError.InProgress, Interop.Error.EINPROGRESS },
    { SocketError.Interrupted, Interop.Error.EINTR },
    { SocketError.InvalidArgument, Interop.Error.EINVAL },
    { SocketError.IOPending, Interop.Error.EINPROGRESS },
    { SocketError.IsConnected, Interop.Error.EISCONN },
    { SocketError.MessageSize, Interop.Error.EMSGSIZE },
    { SocketError.NetworkDown, Interop.Error.ENETDOWN },
    { SocketError.NetworkReset, Interop.Error.ENETRESET },
    { SocketError.NetworkUnreachable, Interop.Error.ENETUNREACH },
    { SocketError.NoBufferSpaceAvailable, Interop.Error.ENOBUFS },
    { SocketError.NoData, Interop.Error.ENODATA },
    { SocketError.NotConnected, Interop.Error.ENOTCONN },
    { SocketError.NotSocket, Interop.Error.ENOTSOCK },
    { SocketError.OperationAborted, Interop.Error.ECANCELED },
    { SocketError.OperationNotSupported, Interop.Error.ENOTSUP },
    { SocketError.ProtocolFamilyNotSupported, Interop.Error.EPFNOSUPPORT },
    { SocketError.ProtocolNotSupported, Interop.Error.EPROTONOSUPPORT },
    { SocketError.ProtocolOption, Interop.Error.ENOPROTOOPT },
    { SocketError.ProtocolType, Interop.Error.EPROTOTYPE },
    { SocketError.Shutdown, Interop.Error.EPIPE },
    { SocketError.SocketNotSupported, Interop.Error.ESOCKTNOSUPPORT },
    { SocketError.Success, Interop.Error.SUCCESS },
    { SocketError.TimedOut, Interop.Error.ETIMEDOUT },
    { SocketError.TooManyOpenSockets, Interop.Error.ENFILE }, // could also have been EMFILE
    { SocketError.TryAgain, Interop.Error.EAGAIN }, // not a perfect mapping, but better than nothing
    { SocketError.WouldBlock, Interop.Error.EAGAIN  },
};

internal static bool TryGetNativeErrorForSocketError(SocketError error, out Interop.Error errno)
{
    return s_socketErrorToNativeError.TryGetValue(error, out errno);
}

internal int RawErrno
{
    get { return _rawErrno == -1 ? (_rawErrno = Interop.Sys.ConvertErrorPalToPlatform(_error)) : _rawErrno; }
}

[DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_ConvertErrorPalToPlatform")]
internal static extern int ConvertErrorPalToPlatform(Error error);

$ errno -ls
EPERM 1 Operation not permitted
ENOENT 2 No such file or directory
ESRCH 3 No such process
EINTR 4 Interrupted system call
EIO 5 Input/output error
ENXIO 6 No such device or address
E2BIG 7 Argument list too long
ENOEXEC 8 Exec format error
EBADF 9 Bad file descriptor
ECHILD 10 No child processes
EAGAIN 11 Resource temporarily unavailable
ENOMEM 12 Cannot allocate memory
EACCES 13 Permission denied
EFAULT 14 Bad address
ENOTBLK 15 Block device required
EBUSY 16 Device or resource busy
EEXIST 17 File exists
EXDEV 18 Invalid cross-device link
ENODEV 19 No such device
ENOTDIR 20 Not a directory
EISDIR 21 Is a directory
EINVAL 22 Invalid argument
ENFILE 23 Too many open files in system
EMFILE 24 Too many open files
ENOTTY 25 Inappropriate ioctl for device
ETXTBSY 26 Text file busy
EFBIG 27 File too large
ENOSPC 28 No space left on device
ESPIPE 29 Illegal seek
EROFS 30 Read-only file system
EMLINK 31 Too many links
EPIPE 32 Broken pipe
EDOM 33 Numerical argument out of domain
ERANGE 34 Numerical result out of range
EDEADLK 35 Resource deadlock avoided
ENAMETOOLONG 36 File name too long
ENOLCK 37 No locks available
ENOSYS 38 Function not implemented
ENOTEMPTY 39 Directory not empty
ELOOP 40 Too many levels of symbolic links
EWOULDBLOCK 11 Resource temporarily unavailable
ENOMSG 42 No message of desired type
EIDRM 43 Identifier removed
ECHRNG 44 Channel number out of range
EL2NSYNC 45 Level 2 not synchronized
EL3HLT 46 Level 3 halted
EL3RST 47 Level 3 reset
ELNRNG 48 Link number out of range
EUNATCH 49 Protocol driver not attached
ENOCSI 50 No CSI structure available
EL2HLT 51 Level 2 halted
EBADE 52 Invalid exchange
EBADR 53 Invalid request descriptor
EXFULL 54 Exchange full
ENOANO 55 No anode
EBADRQC 56 Invalid request code
EBADSLT 57 Invalid slot
EDEADLOCK 35 Resource deadlock avoided
EBFONT 59 Bad font file format
ENOSTR 60 Device not a stream
ENODATA 61 No data available
ETIME 62 Timer expired
ENOSR 63 Out of streams resources
ENONET 64 Machine is not on the network
ENOPKG 65 Package not installed
EREMOTE 66 Object is remote
ENOLINK 67 Link has been severed
EADV 68 Advertise error
ESRMNT 69 Srmount error
ECOMM 70 Communication error on send
EPROTO 71 Protocol error
EMULTIHOP 72 Multihop attempted
EDOTDOT 73 RFS specific error
EBADMSG 74 Bad message
EOVERFLOW 75 Value too large for defined data type
ENOTUNIQ 76 Name not unique on network
EBADFD 77 File descriptor in bad state
EREMCHG 78 Remote address changed
ELIBACC 79 Can not access a needed shared library
ELIBBAD 80 Accessing a corrupted shared library
ELIBSCN 81 .lib section in a.out corrupted
ELIBMAX 82 Attempting to link in too many shared libraries
ELIBEXEC 83 Cannot exec a shared library directly
EILSEQ 84 Invalid or incomplete multibyte or wide character
ERESTART 85 Interrupted system call should be restarted
ESTRPIPE 86 Streams pipe error
EUSERS 87 Too many users
ENOTSOCK 88 Socket operation on non-socket
EDESTADDRREQ 89 Destination address required
EMSGSIZE 90 Message too long
EPROTOTYPE 91 Protocol wrong type for socket
ENOPROTOOPT 92 Protocol not available
EPROTONOSUPPORT 93 Protocol not supported
ESOCKTNOSUPPORT 94 Socket type not supported
EOPNOTSUPP 95 Operation not supported
EPFNOSUPPORT 96 Protocol family not supported
EAFNOSUPPORT 97 Address family not supported by protocol
EADDRINUSE 98 Address already in use
EADDRNOTAVAIL 99 Cannot assign requested address
ENETDOWN 100 Network is down
ENETUNREACH 101 Network is unreachable
ENETRESET 102 Network dropped connection on reset
ECONNABORTED 103 Software caused connection abort
ECONNRESET 104 Connection reset by peer
ENOBUFS 105 No buffer space available
EISCONN 106 Transport endpoint is already connected
ENOTCONN 107 Transport endpoint is not connected
ESHUTDOWN 108 Cannot send after transport endpoint shutdown
ETOOMANYREFS 109 Too many references: cannot splice
ETIMEDOUT 110 Connection timed out
ECONNREFUSED 111 Connection refused
EHOSTDOWN 112 Host is down
EHOSTUNREACH 113 No route to host
EALREADY 114 Operation already in progress
EINPROGRESS 115 Operation now in progress
ESTALE 116 Stale file handle
EUCLEAN 117 Structure needs cleaning
ENOTNAM 118 Not a XENIX named type file
ENAVAIL 119 No XENIX semaphores available
EISNAM 120 Is a named type file
EREMOTEIO 121 Remote I/O error
EDQUOT 122 Disk quota exceeded
ENOMEDIUM 123 No medium found
EMEDIUMTYPE 124 Wrong medium type
ECANCELED 125 Operation canceled
ENOKEY 126 Required key not available
EKEYEXPIRED 127 Key has expired
EKEYREVOKED 128 Key has been revoked
EKEYREJECTED 129 Key was rejected by service
EOWNERDEAD 130 Owner died
ENOTRECOVERABLE 131 State not recoverable
ERFKILL 132 Operation not possible due to RF-kill
EHWPOISON 133 Memory page has hardware error
ENOTSUP 95 Operation not supported

$ errno -ls
EPERM 1 Operation not permitted
ENOENT 2 No such file or directory
ESRCH 3 No such process
EINTR 4 Interrupted system call
EIO 5 Input/output error
ENXIO 6 Device not configured
E2BIG 7 Argument list too long
ENOEXEC 8 Exec format error
EBADF 9 Bad file descriptor
ECHILD 10 No child processes
EDEADLK 11 Resource deadlock avoided
ENOMEM 12 Cannot allocate memory
EACCES 13 Permission denied
EFAULT 14 Bad address
ENOTBLK 15 Block device required
EBUSY 16 Resource busy
EEXIST 17 File exists
EXDEV 18 Cross-device link
ENODEV 19 Operation not supported by device
ENOTDIR 20 Not a directory
EISDIR 21 Is a directory
EINVAL 22 Invalid argument
ENFILE 23 Too many open files in system
EMFILE 24 Too many open files
ENOTTY 25 Inappropriate ioctl for device
ETXTBSY 26 Text file busy
EFBIG 27 File too large
ENOSPC 28 No space left on device
ESPIPE 29 Illegal seek
EROFS 30 Read-only file system
EMLINK 31 Too many links
EPIPE 32 Broken pipe
EDOM 33 Numerical argument out of domain
ERANGE 34 Result too large
EAGAIN 35 Resource temporarily unavailable
EWOULDBLOCK 35 Resource temporarily unavailable
EINPROGRESS 36 Operation now in progress
EALREADY 37 Operation already in progress
ENOTSOCK 38 Socket operation on non-socket
EDESTADDRREQ 39 Destination address required
EMSGSIZE 40 Message too long
EPROTOTYPE 41 Protocol wrong type for socket
ENOPROTOOPT 42 Protocol not available
EPROTONOSUPPORT 43 Protocol not supported
ESOCKTNOSUPPORT 44 Socket type not supported
ENOTSUP 45 Operation not supported
EPFNOSUPPORT 46 Protocol family not supported
EAFNOSUPPORT 47 Address family not supported by protocol family
EADDRINUSE 48 Address already in use
EADDRNOTAVAIL 49 Can`t assign requested address
ENETDOWN 50 Network is down
ENETUNREACH 51 Network is unreachable
ENETRESET 52 Network dropped connection on reset
ECONNABORTED 53 Software caused connection abort
ECONNRESET 54 Connection reset by peer
ENOBUFS 55 No buffer space available
EISCONN 56 Socket is already connected
ENOTCONN 57 Socket is not connected
ESHUTDOWN 58 Can`t send after socket shutdown
ETOOMANYREFS 59 Too many references: can`t splice
ETIMEDOUT 60 Operation timed out
ECONNREFUSED 61 Connection refused
ELOOP 62 Too many levels of symbolic links
ENAMETOOLONG 63 File name too long
EHOSTDOWN 64 Host is down
EHOSTUNREACH 65 No route to host
ENOTEMPTY 66 Directory not empty
EPROCLIM 67 Too many processes
EUSERS 68 Too many users
EDQUOT 69 Disc quota exceeded
ESTALE 70 Stale NFS file handle
EREMOTE 71 Too many levels of remote in path
EBADRPC 72 RPC struct is bad
ERPCMISMATCH 73 RPC version wrong
EPROGUNAVAIL 74 RPC prog. not avail
EPROGMISMATCH 75 Program version wrong
EPROCUNAVAIL 76 Bad procedure for program
ENOLCK 77 No locks available
ENOSYS 78 Function not implemented
EFTYPE 79 Inappropriate file type or format
EAUTH 80 Authentication error
ENEEDAUTH 81 Need authenticator
EPWROFF 82 Device power is off
EDEVERR 83 Device error
EOVERFLOW 84 Value too large to be stored in data type
EBADEXEC 85 Bad executable (or shared library)
EBADARCH 86 Bad CPU type in executable
ESHLIBVERS 87 Shared library version mismatch
EBADMACHO 88 Malformed Mach-o file
ECANCELED 89 Operation canceled
EIDRM 90 Identifier removed
ENOMSG 91 No message of desired type
EILSEQ 92 Illegal byte sequence
ENOATTR 93 Attribute not found
EBADMSG 94 Bad message
EMULTIHOP 95 EMULTIHOP (Reserved)
ENODATA 96 No message available on STREAM
ENOLINK 97 ENOLINK (Reserved)
ENOSR 98 No STREAM resources
ENOSTR 99 Not a STREAM
EPROTO 100 Protocol error
ETIME 101 STREAM ioctl timeout
EOPNOTSUPP 102 Operation not supported on socket
ENOPOLICY 103 Policy not found
ENOTRECOVERABLE 104 State not recoverable
EOWNERDEAD 105 Previous owner died
EQFULL 106 Interface output queue is full
ELAST 106 Interface output queue is full

public override int ErrorCode {
    //
    // the base class returns the HResult with this property
    // we need the Win32 Error Code, hence the override.
    //
    get {
        return NativeErrorCode;
    }
}

public override int ErrorCode => base.NativeErrorCode;

protected virtual bool ShouldRetryConnection(Exception ex)
{
    if (ex is SocketException sx)
        return sx.SocketErrorCode == SocketError.ConnectionRefused;
    return false;
}

var allErrors = Enum.GetValues(typeof(SocketError)).Cast<SocketError>().ToList();
var maxNameWidth = allErrors.Select(x => x.ToString().Length).Max();
foreach (var socketError in allErrors)
{
    var name = socketError.ToString().PadRight(maxNameWidth);
    var code = new SocketException((int) socketError).NativeErrorCode.ToString().PadLeft(7);
    Console.WriteLine("| {name} | {code} |");
}

Содержание

1. Troubleshooting connection issues
2. Problem: the socket is not able to connect​
3. You are trying to reach a plain WebSocket server​
4. The server is not reachable​
5. The client is not compatible with the version of the server​
6. The server does not send the necessary CORS headers​
7. You didn’t enable sticky sessions (in a multi server setup)​
8. The request path does not match on both sides​
9. Problem: the socket gets disconnected​
10. The browser tab was minimized and heartbeat has failed​
11. The client is not compatible with the version of the server​
12. You are trying to send a huge payload​
13. Problem: the socket is stuck in HTTP long-polling​
14. Server API
15. Server​
16. new Server(httpServer [, options] )​
17. new Server(port [, options] )​
18. How Socket Error Codes Depend on Runtime and Operating System
19. Sockets and error codes
20. Digging into the problem
21. SocketErrorCode
22. NativeErrorCode
23. ErrorCode
24. Writing cross-platform socket error handling
25. Overview of the native error codes
26. Summary