Network identifiers are used by the ReoLive engine to uniquely identify networks and elements inside of networks, such as components, connectors and ports. A network identifier consist of 1-3 positive integers, separated by a colon (' : '). The first integer is the unique ID of a network. The second ID identifies either a component or a connector inside that network. The third ID is used to access ports of a component.
An important application of network identifiers is the coordination web service provided by the ReoLive engine. Suppose you have a component in a network with a number of source and sink ports, which are hooked up to a connector. In the implementation of your component you instantiate these ports using their network identifier. Internally, a source port with an ID, say 1:2:0, is mapped to a web service for source ports located at http://reo.project.cwi.nl/live/sources/1:2:0 -- so the network identifier is used in the web service URL to identify the port used for the communication.
Important: Network identifiers are assigned automatically by the server. You don't need to specify them in your Reo files. You can also upload the same file twice and you will get the same network twice, but with different IDs.