By default all WCF will operated in the Request-Replay mode. It means that, when client make a request to the WCF service and client will wait to get response from service (till receiveTimeout). After getting the response it will start executing the rest of the statement. If service doesn't respond to the service within receiveTimeout, client will receive TimeOutException.
Apart from NetPeerTcpBinding and the NetMsmqBinding all other bindings will support request-reply operations.