Connection closed error when calling SOAP API from C#

Question

I am calling Salesforce SOAP API from C#. There are multiple instances of the .NET process running which results in concurrent SOAP API calls being made to Salesforce.

Some of the calls are failing with error - System.Net.WebException The underlying connection was closed: A connection that was expected to be kept alive was closed by the server.

I have observed that this error occurs only during the peak times when large number of SOAP API calls are being made.

I am using proxy class generated using old "Add Web Reference" method in C# instead WCF way of "Add Service Reference". So there is no explicit binding configuration that I am using for my C# proxy class.

any idea why this error might be happening ?

Answer 1

There is a Concurrent API Request Limit. Can you track how many calls are being made simultaneously when the error occurs and how long they were running for? If it is this limit you are exceeding you could implement some form of queuing to throttle the requests.

Concurrent API Request Limits

The following table lists the limits for various types of organizations for concurrent requests (calls) with a duration of 20 seconds or longer.

Organization Type           Limit
Developer Edition           5
Trial organizations         5
Production organizations    25
Sandbox                     25