WCF Max Instances seems to be limited to 10

Question

I have a simple WCF service hosted in IIS7.5 exposed over a wsHttp binding using message security and InstanceContextMode.PerCall

I have a simple UI that spins up a

Answer 1

The MaxConcurrentSessions documentation mentions an optimization for client requests that come from the same AppDomain. Your sample code is basically hitting the same socket on the service. Since there is some throttling done per client, that may be affecting your service behavior. Also, 10 happens to be the default value for MaxConcurrentSessions so it may be that your config is not changing the WCF default value.

Enabling security affects the total threads because it establishes a "session" per client so that each request sent does not need to be authenticated on every call. Those security "sessions" count toward the MaxConcurrentSessions total.