An existing connection was forcibly closed by the remote host

Question

I am working with a commercial application which is throwing a SocketException with the message      An existing connection was forcibly closed by the remote host   This happens with a socket connection between client and server  The connection is alive and well  and heaps of data is being transferred  but it then becomes disconnected out of nowhere   Has anybody seen this before  What could the causes be  I can kind of guess a few causes  but also is there any way to add more into this code to work out what the cause could be   Any comments   ideas are welcome       The latest      I have some logging from some  NET tracing   System Net Sockets Verbose  0    8188  Socket 30180123  Send   DateTime 2010-04-07T20 49 48 6317500Z  System Net Sockets Error  0    8188  Exception in the Socket 30180123  Send - An existing connection was forcibly closed by the remote host DateTime 2010-04-07T20 49 48 6317500Z   System Net Sockets Verbose  0    8188  Exiting Socket 30180123  Send   - gt  0 0   Based on other parts of the logging I have seen the fact that it says  0 0  means a packet of 0 bytes length is being sent  But what does that really mean   One of two possibilities is occuring  and I am not sure which   1  The connection is being closed  but data is then being written to the socket  thus creating the exception above  The 0 0 simply means that nothing was sent because the socket was already closed   2  The connection is still open  and a packet of zero bytes is being sent  i e  the code has a bug  and the 0 0 means that a packet of zero bytes is trying to be sent   What do you reckon  It might be inconclusive I guess  but perhaps someone else has seen this kind of thing

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If Running In A  Net 4 5 2 Service For me the issue was compounded because the call was running in a  Net 4 5 2 service  I followed  willmaz suggestion but got a new error  In running the service with logging turned on  I viewed the handshaking with the target site would initiate ok  and send the bearer token  but on the following step to process the Post call  it would seem to drop the auth token and the site would reply with Unauthorized  Solution It turned out that the service pool credentials did not have rights to change TLS     and when I put in my local admin account into the pool  it all worked

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Using TLS 1 2 solved this error  You can force your application using TLS 1 2 with this  make sure to execute it before calling your service     ServicePointManager SecurityProtocol   SecurityProtocolType Tls12    Another solution   Enable strong cryptography in your local machine or server in order to use TLS1 2 because by default it is disabled so only TLS1 0 is used  To enable strong cryptography   execute these commande in PowerShell with admin privileges    Set-ItemProperty -Path  HKLM  SOFTWARE Wow6432Node Microsoft  NetFramework v4 0 30319  -Name  SchUseStrongCrypto  -Value  1  -Type DWord Set-ItemProperty -Path  HKLM  SOFTWARE Microsoft  NetFramework v4 0 30319  -Name  SchUseStrongCrypto  -Value  1  -Type DWord    You need to reboot your computer for these changes to take effect

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This is not a bug in your code  It is coming from  Net s Socket implementation  If you use the overloaded implementation of EndReceive as below you will not get this exception       SocketError errorCode      int nBytesRec   socket EndReceive ar  out errorCode       if  errorCode    SocketError Success                nBytesRec   0

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I had the same issue and managed to resolve it eventually  In my case  the port that the client sends the request to did not have a SSL cert binding to it  So I fixed the issue by binding a SSL cert to the port on the server side  Once that was done  this exception went away

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This generally means that the remote side closed the connection  usually by sending a TCP IP RST packet   If you re working with a third-party application  the likely causes are    You are sending malformed data to the application  which could include sending an HTTPS request to an HTTP server  The network link between the client and server is going down for some reason You have triggered a bug in the third-party application that caused it to crash The third-party application has exhausted system resources   It s likely that the first case is what s happening   You can fire up Wireshark to see exactly what is happening on the wire to narrow down the problem   Without more specific information  it s unlikely that anyone here can really help you much

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For anyone getting this exception while reading data from the stream  this may help  I was getting this exception when reading the HttpResponseMessage in a loop like this   using  var remoteStream   await response Content ReadAsStreamAsync    using  var content   File Create DownloadPath         var buffer   new byte 1024       int read       while   read   await remoteStream ReadAsync buffer  0  buffer Length      0                await content WriteAsync buffer  0  read           await content FlushAsync              After some time I found out the culprit was the buffer size  which was too small and didn t play well with my weak Azure instance  What helped was to change the code to   using  Stream remoteStream   await response Content ReadAsStreamAsync    using  FileStream content   File Create DownloadPath         await remoteStream CopyToAsync content       CopyTo   method has a default buffer size of 81920  The bigger buffer sped up the process and the errors stopped immediately  most likely because the overall download speeds increased  But why would download speed matter in preventing this error   It is possible that you get disconnected from the server because the download speeds drop below minimum threshold the server is configured to allow  For example  in case the application you are downloading the file from is hosted on IIS  it can be a problem with http sys configuration    Http sys is the http protocol stack that IIS uses to perform http communication with clients   It has a timer called MinBytesPerSecond that is responsible for killing a connection if its transfer rate drops below some kb sec threshold   By default  that threshold is set to 240 kb sec     The issue is described in this old blogpost from TFS development team and concerns IIS specifically  but may point you in a right direction  It also mentions an old bug related to this http sys attribute  link  In case you are using Azure app services and increasing the buffer size does not eliminate the problem  try to scale up your machine as well  You will be allocated more resources including connection bandwidth

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I ve got this exception because of circular reference in entity In entity that look like  public class Catalog       public int Id   get  set        public int ParentId   get  set        public Catalog Parent   get  set        public ICollection lt Catalog gt  ChildCatalogs   get  set        I added  IgnoreDataMemberAttribute  to the Parent property  And that solved the problem

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I got the same issue while using  NET Framework 4 5  However  when I update the  NET version to 4 7 2 connection issue was resolved  Maybe this is due to SecurityProtocol support issue

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This error occurred in my application with the CIP-protocol whenever I didn t Send or received data in less than 10s    This was caused by the use of the forward open method  You can avoid this by working with an other method  or to install an update rate of less the 10s that maintain your forward-open-connection

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I had this issue when i tried to connect to postgresql while i m using microsoft sutdio for mssql

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Had the same bug  Actually worked in case the traffic was sent using some proxy  fiddler in my case   Updated  NET framework from 4 5 2  to   4 6 and now everything works fine  The actual request was  new WebClient   DownloadData  URL    The exception was         SocketException  An existing connection was forcibly closed by the   remote host

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Simple solution for this common annoying issue    Just go to your   context cs  file  located under   context tt  which located under your    edmx  file     Then  add this line to your constructor    public DBEntities              base  name DBEntities                   this Configuration ProxyCreationEnabled   false     ADD THIS LINE           hope this is helpful

[c#] An existing connection was forcibly closed by the remote host

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