Unable to read data from the transport connection An existing connection was forcibly closed by the remote host

Question

I have a server app and sometimes  when the client tries to connect  I get the following error      NOTE  the  couldn t get stream from client or login failed  is a text that s added by me in catch statement  and the line at which it stops   sThread   line 96   is     tcpClient    TcpClient client  clientStream   tcpClient GetStream    sr   new StreamReader clientStream   sw   new StreamWriter clientStream       line 96                   a   sr ReadLine      What may be causing this problem  Note that it doesn t happen all the time

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This won t help for intermittent issues  but may be useful for other people with a similar problem    I had cloned a VM and started it up on a different network with a new IP address but not changed the bindings in IIS  Fiddler was showing me  Unable to read data from the transport connection  An existing connection was forcibly closed by the remote host  and IE was telling me  Turn on TLS 1 0  TLS 1 1  and TLS 1 2 in Advanced settings   Changing the binding to the new IP address solved it for me

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We had a very similar issue whereby a client s website was trying to connect to our Web API service and getting that same message  This started happening completely out of the blue when there had been no code changes or Windows updates on the server where IIS was running   In our case it turned out that the calling website was using a version of  Net that only supported TLS 1 0 and for some reason the server where our IIS was running stopped appeared to have stopped accepting TLS 1 0 calls   To diagnose that we had to explicitly enable TLS via the registry on the IIS s server and then restart that server   These are the reg keys    HKEY LOCAL MACHINE SYSTEM CurrentControlSet Control SecurityProviders SCHANNEL Protocols TLS     1 0 Client   DisabledByDefault  dword 00000000  Enabled  dword 00000001       HKEY LOCAL MACHINE SYSTEM CurrentControlSet Control SecurityProviders SCHANNEL Protocols TLS     1 0 Server   DisabledByDefault  dword 00000000  Enabled  dword 00000001       HKEY LOCAL MACHINE SYSTEM CurrentControlSet Control SecurityProviders SCHANNEL Protocols TLS     1 1 Client   DisabledByDefault  dword 00000000  Enabled  dword 00000001       HKEY LOCAL MACHINE SYSTEM CurrentControlSet Control SecurityProviders SCHANNEL Protocols TLS     1 1 Server   DisabledByDefault  dword 00000000  Enabled  dword 00000001       HKEY LOCAL MACHINE SYSTEM CurrentControlSet Control SecurityProviders SCHANNEL Protocols TLS     1 2 Client   DisabledByDefault  dword 00000000  Enabled  dword 00000001       HKEY LOCAL MACHINE SYSTEM CurrentControlSet Control SecurityProviders SCHANNEL Protocols TLS     1 2 Server   DisabledByDefault  dword 00000000  Enabled  dword 00000001  If that doesn t do it  you could also experiment with adding the entry for SSL 2 0         HKEY LOCAL MACHINE SYSTEM CurrentControlSet Control SecurityProviders SCHANNEL Protocols SSL 2 0 Client       DisabledByDefault  dword 00000000      Enabled  dword 00000001       HKEY LOCAL MACHINE SYSTEM CurrentControlSet Control SecurityProviders SCHANNEL Protocols SSL 2 0 Server       DisabledByDefault  dword 00000000      Enabled  dword 00000001   My answer to another question here has this powershell script that we used to add the entries   NOTE  Enabling old security protocols is not a good idea  the right answer in our case was to get the client website to update it s code to use TLS 1 2  but the registry entries above can help diagnose the issue in the first place

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System Net ServicePointManager Expect100Continue   false    This issue sometime occurs due the reason of proxy server implemented on web server  To bypass the proxy server by putting this line before calling the send service

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For some reason  the connection to the server was lost  It could be that the server explicitly closed the connection  or a bug on the server caused it to be closed unexpectedly  Or something between the client and the server  a switch or router  dropped the connection   It might be server code that caused the problem  and it might not be  If you have access to the server code  you can put some debugging in there to tell you when client connections are closed   That might give you some indication of when and why connections are being dropped   On the client  you have to write your code to take into account the possibility of the server failing at any time   That s just the way it is  network connections are inherently unreliable

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I experienced the error with python clr running mdx query to Microsoft analytic services using adomd I solved it with help of Hans Vonn and here is the python version  clr AddReference  quot System Net quot   from System Net import ServicePointManager  SecurityProtocolType  ServicePointManager SecurityProtocol   SecurityProtocolType Ssl3   SecurityProtocolType Tls12   SecurityProtocolType Tls11   SecurityProtocolType Tls

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Another option would be to check the error code generated using try-catch block and first catching a WebException   In my case  the error code was  SendFailure  because of certificate issue on HTTPS url  once I hit HTTP  that got resolved   https   docs microsoft com en-us dotnet api system net webexceptionstatus redirectedfrom MSDN amp view netframework-4 8

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Had a similar problem and was getting the following errors depending on what app I used and if we bypassed the firewall   load balancer or not      HTTPS handshake to  blah   for  136  failed    System IO IOException Unable to read data from the transport   connection  An existing connection was forcibly closed by the remote   host   and     ReadResponse   failed  The server did not return a complete response for this request  Server returned 0 bytes                                                                                                                                                                                                                                                                                                                                                                                                           The problem turned out to be that the SSL Server Certificate got missed and wasn t installed on a couple servers

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If you have a https certificate on the domain  make sure you have the https binding to the domain name in IIS  In IIS -  Select your domain -  Click on Bindings  Site Bindings Window opens up  Add a binding for https

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My specific case scenario was that the Azure app service had the minimum TLS version changed to 1 2  I don t know if that s the default from now on  but changing it back to 1 0 made it work   You can access the setting inside  SSL Settings

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I had a Third Party application  Fiddler  running to try and see the requests being sent  Closing this application fixed it for me

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Calls to HTTPS services from one of our servers were also throwing the  Unable to read data from the transport connection   An existing connection was forcibly closed  exception   HTTP service  though  worked fine   Used Wireshark to see that it was a TLS handshake Failure   Ended up being that the cipher suite on the server needed to be updated

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I received this error when calling a web-service  The issue was also related to transport level security  I could call the web-service through a website project  but when reusing the same code in a test project I would get a WebException that contained this message  Adding the following line before making the call resolved the issue   System Net ServicePointManager SecurityProtocol   SecurityProtocolType Tls   SecurityProtocolType Tls11   SecurityProtocolType Tls12    Edit     System Net ServicePointManager SecurityProtocol - This property   selects the version of the Secure Sockets Layer  SSL  or Transport   Layer Security  TLS  protocol to use for new connections that use the   Secure Hypertext Transfer Protocol  HTTPS  scheme only  existing   connections are not changed    I believe the SecurityProtocol configuration is important during the TLS handshake when selecting the protocol version       TLS handshake - This protocol is used to exchange all the information required by both sides for the exchange of the actual application data by TLS       ClientHello - A client sends a ClientHello message specifying the highest TLS protocol version it supports          ServerHello - The server responds with a ServerHello message  containing the chosen protocol version     The chosen protocol version should be the highest that both the client and server support  For example  if the client supports TLS version 1 1 and the server supports version 1 2  version 1 1 should be selected  version 1 2 should not be selected

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Not sure which of the fixes in these blog posts helped  but one of them sorted this issue for me      http   briancaos wordpress com 2012 07 06 unable-to-read-data-from-the-transport-connection-the-connection-was-closed   The trick that helped me was to quit using a WebRequest and use a HttpWebRequest instead  The HttpWebRequest allows me to play with 3 important settings   and  http   briancaos wordpress com 2012 06 15 an-existing-connection-was-forcibly-closed-by-the-remote-host    STEP 1  Disable KeepAlive  STEP 2  Set ProtocolVersion to Version10 STEP 3  Limiting the number of service points

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For me  It was an issue where in the IIS binding it had the IP address of the web server  I changed it to use all unassigned IPs and my application started to work

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This solved my problem  I added this line before the request is made   System Net ServicePointManager Expect100Continue   false    It seemed there were a proxy in the way of the server that not supported 100-continue behavior

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I try to perform a TLS1 2 connection  I tried eveything mention above but didn t work  Do you have any additional idea  String WebserviceApiURL    quot https   soapServiceURL quot    Uri uri   new Uri WebserviceApiURL   HttpWebRequest request    HttpWebRequest WebRequest Create uri   request Method    quot GET quot   request ContentType    quot application json quot   request Headers Add  quot Token quot    quot xxxxxx quot     System Net ServicePointManager SecurityProtocol   SecurityProtocolType Tls   SecurityProtocolType Tls11   SecurityProtocolType Tls12  System Net ServicePointManager Expect100Continue   false   request KeepAlive   false  request ProtocolVersion   HttpVersion Version10  request ServicePoint ConnectionLimit   1   WebResponse response   request GetResponse

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For those who may find this later  after  NET version 4 6  I was running into this problem as well  Make sure that you check your web config file for the following lines   lt compilation debug  quot true quot  targetFramework  quot 4 5 quot  gt       lt httpRuntime targetFramework  quot 4 5 quot    gt   If you are running 4 6 x or a higher version of  NET on the server  make sure you adjust these targetFramework values to match the version of the framework on your server  If your versions read less than 4 6 x  then I would recommend you upgrade  NET and use the newer version unless your code is dependent on an older version  which  in that case  you should consider updating it   I changed the targetFrameworks to 4 7 2 and the problem disappeared   lt compilation debug  quot true quot  targetFramework  quot 4 7 2 quot  gt       lt httpRuntime targetFramework  quot 4 7 2 quot    gt   The newer frameworks sort this issue out by using the best protocol available and blocking insecure or obsolete ones  If the remote service you are trying to connect to or call is giving this error  it could be that they don t support the old protocols anymore

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I get that problem in the past  I m using PostgreSQL and when I run my program  sometimes it connects and sometimes it throws an error like that   When I experiment with my code  I put my Connection code at the very first line below the public Form  Here is an example   BEFORE       public Form1                       HERE LIES SOME CODES FOR RESIZING MY CONTROLS DURING RUNTIME           CODE           CODE AGAIN           ANOTHER CODE           CODE NA NAMAN           CODE PA RIN                 Connect to Database to generate auto number         NpgsqlConnection iConnect   new NpgsqlConnection  Server localhost Port 5432 User ID postgres Password pass Database DB            iConnect Open            NpgsqlCommand iQuery   new NpgsqlCommand  Select   from table1   iConnect           NpgsqlDataReader iRead   iQuery ExecuteReader            NpgsqlDataAdapter iAdapter   new NpgsqlDataAdapter iQuery            DataSet iDataSet   new DataSet            iAdapter Fill iDataSet   ID             MessageBox Show iDataSet Tables  ID   Rows Count ToString                 NOW       public Form1                       Connect to Database to generate auto number         NpgsqlConnection iConnect   new NpgsqlConnection  Server localhost Port 5432 User ID postgres Password pass Database DB            iConnect Open            NpgsqlCommand iQuery   new NpgsqlCommand  Select   from table1   iConnect           NpgsqlDataReader iRead   iQuery ExecuteReader            NpgsqlDataAdapter iAdapter   new NpgsqlDataAdapter iQuery            DataSet iDataSet   new DataSet            iAdapter Fill iDataSet   ID             MessageBox Show iDataSet Tables  ID   Rows Count ToString                    HERE LIES SOME CODES FOR RESIZING MY CONTROLS DURING RUNTIME           CODE           CODE AGAIN           ANOTHER CODE           CODE NA NAMAN           CODE PA RIN               I think that the program must read first the connection before doing anything  I don t know  correct me if I m wrong  But according to my research  it s not a code problem - it was actually from the machine itself   Happy Coding

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The reason this was happening to me was I had a recursive dependency in my DI provider  In my case I had   services AddScoped provider   gt  new CfDbContext builder Options    services AddScoped provider   gt  provider GetService lt CfDbContext gt        Fix was to just remove the second scoped service registration  services AddScoped provider   gt  new CfDbContext builder Options

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This error usually means that the target machine is running  but the service that you re trying to connect to is not available    Either it stopped  crashed  or is busy with another request    In English  The connection to the machine  remote host server PC that the service runs at  was made but since the service was not available on that machine  the machine didn t know what to do with the request   If the connection to the machine was not available  you d see a different error   I forget what it is  but it s along the lines of  Service Unreachable   or  Unavailable    Edit - added  It IS possible that this is being caused by a firewall blocking the port  but given that you say it s intermittent   sometimes when the client tries to connect    that s very unlikely   I didn t include that originally because I had ruled it out mentally before replying

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Try checking if you can establish handshake in the first place  I had this issue before when uploading a file and I only figured out that the issue was the nonexistent route when I removed the upload and checked if it can login given the parameters

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According to  Hans Vonn  replies   Adding the following line before making the call resolved the issue   System Net ServicePointManager SecurityProtocol   SecurityProtocolType Tls   SecurityProtocolType Tls11   SecurityProtocolType Tls12    After adding Security protocol and working fine but I have to add before every API call which is not healthy  I just upgrade  net framework version at least 4 6 and working as expected do not require to adding before every API call

[c#] Unable to read data from the transport connection : An existing connection was forcibly closed by the remote host

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