During message handling an endpoint is expected to be able to connect to external resources, such as remote services via HTTP.
If the endpoint is hosted in a process outside IIS, such as a Windows Service, by default the .NET Framework allows 2 concurrent outgoing HTTP requests per process. This can be a limitation on the overall throughput of the endpoint itself that ends up having outgoing HTTP requests queued and, as a consequence, a limitation in its ability to process incoming messages.
It is possible to change the default connection limit of a process via the static DefaultConnectionLimit property of the ServicePointManager class, as in the following sample:
ServicePointManager.DefaultConnectionLimit = 10;The above code can be placed in the process startup.
See ServicePointManager on MSDN for more information.