General method (works also for HTTP)
BizTalk enables users to configure WCF host to limit the maximum connections to a particular address.
The connectionManagement element in the btsntsvc.config file is designed to specify the number of connections to a given address. By default BizTalk allows for 2 connections for any given WCF host.
How to limit number of connections
https://stackoverflow.com/questions/3591283/biztalk-how-to-limit-number-of-connections-to-a-wcf-service
Throttling
https://docs.microsoft.com/en-us/biztalk/technical-guides/optimizing-biztalk-server-wcf-adapter-performance
Add the ServiceThrottlingBehavior service behavior to a WCF-Custom or WCF-CustomIsolated Receive Location and use the following settings: