The underlying connection was closed — API endpoint call fails

Question

I'm trying to determine why a call to a Restful API endpoint is failing when I use HTTPS but not HTTP from a Windows Server 2012 R2. The same HTTPS call works when I run the application locally on my laptop (Windows 7).

Unfortunately I cannot get Fiddler to show the calls made from the application on the Web Server to the API. The AppContainer Loopback Exemption Utility errors trying to enumerate the AppContainers list. The Server is also locked down by group policies, so I can't turnoff the firewall to try to resolve the Fiddler issue.

The call to the API is:

public Task<HttpResponseMessage> SendAsync(HttpRequestMessage request)
{
  client = new HttpClient();

  // removed code for setting ignoreCertErrors and environmentName

  if (ignoreCertErrors && environmentName.ToUpper() != "PROD")
            {
                ServicePointManager.ServerCertificateValidationCallback =    delegate { return true; };
            }

  return client.SendAsync(request);
}

Errors received:

================================================================= Message: The underlying connection was closed: An unexpected error occurred on a send. Stack Trace:
at System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
at System.Net.Http.HttpClientHandler.GetResponseCallback(IAsyncResultar)

================================================================= Message: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. Stack Trace:
at System.Net.TlsStream.EndWrite(IAsyncResult asyncResult)
at System.Net.ConnectStream.WriteHeadersCallback(IAsyncResult ar)

================================================================= Message: An existing connection was forcibly closed by the remote host Stack Trace:
at System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult)
at System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult)

=================================================================

How can obtain more detail? I'm trying to avoid low level tools such as Wireshark, I'm hoping there is option trace/log/capture more detail about the application calls to API that are failing.

UPDATE - Here is the tracing information when it fails:

System.Net Information: 0 : [2292] SecureChannel#49584532::.ctor(hostname=XX.XX.com, clientCertificates=0, encryptionPolicy=RequireEncryption)

System.Net Information: 0 : [2292] SecureChannel#49584532 - Left with 0 client certificates to choose from.

System.Net Information: 0 : [2292] Using the cached credential handle. System.Net Information: 0 : [2292] InitializeSecurityContext(credential = System.Net.SafeFreeCredential_SECURITY, context = (null), targetName = XX.XX.com, inFlags = ReplayDetect, SequenceDetect, Confidentiality, AllocateMemory, InitManualCredValidation) System.Net Information: 0 : [2292] InitializeSecurityContext(In-Buffer length=0, Out-Buffer length=178, returned code=ContinueNeeded).

System.Net.Sockets Verbose: 0 : [2292] Socket#14347911::BeginSend()

System.Net.Sockets Verbose: 0 : [2292] Exiting Socket#14347911::BeginSend() -> OverlappedAsyncResult#19699911 System.Net.Sockets Verbose: 0 : [2292] Data from Socket#14347911::PostCompletion

[ Removed ]

System.Net.Sockets Verbose: 0 : [2292] Socket#14347911::EndSend(OverlappedAsyncResult#19699911)

System.Net.Sockets Verbose: 0 : [2292] Exiting Socket#14347911::EndSend() -> Int32#178

System.Net.Sockets Verbose: 0 : [2292] Socket#14347911::BeginReceive()

System.Net.Sockets Verbose: 0 : [2292] Exiting Socket#14347911::BeginReceive() -> OverlappedAsyncResult#2389992

System.Net.Sockets Verbose: 0 : [2292] Socket#14347911::EndReceive(OverlappedAsyncResult#2389992)

System.Net.Sockets Error: 0 : [2292] Socket#14347911::UpdateStatusAfterSocketError() - ConnectionReset

System.Net.Sockets Error: 0 : [2292] Exception in Socket#14347911::EndReceive - An existing connection was forcibly closed by the remote host. System.Net.Sockets Verbose: 0 : [2292] Exiting Socket#14347911::EndReceive() -> Int32#0

System.Net.Sockets Verbose: 0 : [2292] Socket#14

The call to the api is probably failing. When you connect to the Server you are running with guest privileges which do not normally have the credentials to run an api on the server. The api has to be installed on server to run with admin privileges. To verify I'm correct I would check the event viewer on the server to get more details on the error. — jdweng
The same call to the API using HTTP works, but when I switch the API URI use HTTPS it throws the errors above. — Josh
Do you test for null responses? Not sure the root cause, but I suspect you may be getting empty packets. — jdweng
It is the exact same call to the API endpoint, HTTP works but HTTPS fails from the server. HTTPS API calls works locally with the same code. Not sure how handling nulls would be an issue. — Josh

Josh Josh · Accepted Answer · 2016-08-13T19:45:43

The log entry:

System.Net.Sockets Error: 0 : [2292] Socket#14347911::UpdateStatusAfterSocketError() - ConnectionReset

was caused by a Firewall that was blocking the port. Once a new firewall rule was added, the problem was resolved.

The underlying connection was closed — API endpoint call fails

1 Answers