3.1.5.4.12 USER_EVENT Message
The syntax of this message is specified in section 2.2.2.12.
This message is targeted to a client's RunspacePool. The server sends this message to notify a client about a server-side event. Note that the PowerShell Remoting Protocol does not generate or interpret any events; it merely provides a mechanism for higher layers on the client to be notified when new events are reported by the server.
The client's RunspacePool MUST be in an Opened state while processing this message.