The underlying connection was closed: An unexpected error occurred on a receive

转自:

http://www.outsystems.com/forums/discussion/15641/tip-the-underlying-connection-was-closed-an-unexpected-error-occurred-on-a-rece/

Symptom

You application is making a call to another system performing an HTTP(S) request. This request can be a:

• Web service call (SOAP or REST)
• A request to a specific web-page
• Sending an email
• ...

The call is failing and an error occurs in the application. In the Error Log you see an entry similar to (below example is for a SOAP web-reference):

[1] The underlying connection was closed: An unexpected error occurred on a receive.

   at System.Web.Services.Protocols.WebClientProtocol.GetWebResponse(WebRequest request)

   at System.Web.Services.Protocols.HttpWebClientProtocol.GetWebResponse(WebRequest request)

   at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)

   at ssCRMApp.WRefPeopleLookup.WRefPeopleLookup.SearchByName(String search)

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

   at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)

   at System.Net.PooledStream.Read(Byte[] buffer, Int32 offset, Int32 size)

   at System.Net.Connection.SyncRead(HttpWebRequest request, Boolean userRetrievedStream, Boolean probeRead)

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

   at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)

Cause
Errors like these happen because the remote server (to which the call was being made) did not deliver a response to your request and cut the connection before an answer could be sent. Meaning:

1. Your application (the caller) sent the request
2. While the application was waiting for the response, the remote server cut the connection.

Resolution
Resolving such a problem cannot be done on the caller side (your application) - you need to work with the party that provides the service for you.

If you are the other party or want to help: common causes on the other side for these errors are:

• The request is taking too long to run and the server "times it out". If another OutSystems Platform is on the receiving end (meaning: the web call is to an OutSystems Platform) you may want to look here.
• The remote server is having issues. E.g. application pool recycling or crashes that interrupt logic that may be runnning.
• A network layer is cutting the network connection half-way. You may see errors in the remote server similar to this one (e.g. "could not flush response);