The messages/notifications between two ServiceHosts

it classiq

I have similar code on server hosting-side:
(The hosting-part of code is very simplistic)

// Creation ServiceHost #1.
serviceFirst = new ServiceHost(typeof(DomainServiceFirst));
// Waiting for incoming message
serviceFirst.Open();

// Creation ServiceHost #2.
serviceSecond = new ServiceHost(typeof(DomainServiceSecond));
// Waiting for incoming message
serviceSecond.Open();

I need to send and receive the messages/notifications about the model-changes between DomainServiceFirst and DomainServiceSecond.
During the life-time DomainServiceFirst or DomainServiceSecond is activated several changes in the part’s of general model :

DomainServiceFirst => DomainModelFirst (the part of general model);

DomainServiceSecond => DomainModelSecond (the part of general model too)

In the same time the General model is consist of DomainModelFirst & DomainModelSecond

Each of services (DomainServiceFirst and DomainServiceSecond ) are decorated :

\[ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Multiple, 
InstanceContextMode = InstanceContextMode.PerSession, 
IncludeExceptionDetailInFaults = true)\]

My question is:
Is it exists some specifically approach inside WCF-technology for do that (woks with an messages/notifications); if it so, can you please share some internet-links with best-practice examples. Thank you.