A system and method for asynchronous processing of network communications between a client device and a respective synchronous web service. The system and method comprises: an input for receiving a subscription request; a subscription module configured for processing the received subscription request to identify subscription request data in the subscription request for sending in a synchronous request message to the synchronous web service, to identify a notification filter expression in the subscription request for determining whether a synchronous response message received from the synchronous web service in response to the synchronous request message satisfies the subscription request data, and to identify a polling protocol in the subscription request for defining communication parameters of the respective synchronous request and response messages; and an output for sending the polling protocol and the subscription request data to be used in polling the synchronous web service.