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:

Your application (the caller) sent the request
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);