Thanks Eskimo Exactly how you do that depends on the API you’re using (C vs NSXPCConnection), the semantics of your protocol, and design decisions that you have to make for yourself. If you care to share some details, I can elaborate. I was goin for a NSXPCConnection, but this can be changed, the semantic is simple, the XPC Service will connect to network and receive updates over time with a bunch of simple data encoded, best bid price (double), best ask price (double), and reference. The idea is that when the service establish a websocket connection receive the data, decoded, and then send it to the main app as soon as he can, the data is not a batch, will have several updates over time. or can I make a request and reply it only when the app/service is closed? I mean, can I start the Service with a request, and forget about it until an error or connection is received? i don't now if there is a max time for a response, if there isn't, I can start the service, keep the transaction open until I receive a fatal message o when the service can be disconnected? Thanks in advance