2 ms·

Does it do protocol negotiation? i.e. can a client ask the server what interfaces it implements?

• kentonv 9y ago
  There are a few answers to that: 1. If you have a remote object reference, you can (explicitly) cast it to any interface type, and then attempt to call it. If it doesn't implement that interface (or that method), an "unimplemented" exception will be thrown back. It's relatively common to do feature detection this way. 2. It's easy for the application to define a Cap'n Proto interface to support fancier negotiation. For example, you could have all your RPC interfaces extend a common base interface which has a method getSchema() which returns the full interface schema, or a list of interface IDs, or whatever it is you want. 3. We actually plan to bake in schema queries in a future version, such that all objects will support some sort of getSchema() call implicitly. This would especially be useful for clients in dynamic languages that could potentially connect to a server without having a schema at all, and load everything dynamically.