It sounds like you want to use one of the connectors in GeoEvent that has a name like "Receive XXXX on a REST Endpoint". There's several of those that can parse different data formats (Features, JSON, etc.) The connection properties allow you to specify the last part of the url where the GeoEvent process will listen for data from a client. By default, it listens on port 6180 for un-encrypted (http) traffic, and port 6143 for encrypted (https) traffic. Ming Zhao might have additional input on this.
