| To do so, this tutorial implements the `EchoLauncher` protocol from the |
| [fuchsia.examples library](/examples/fidl/fuchsia.examples/): |
| |
| ```fidl |
| {%includecode gerrit_repo="fuchsia/fuchsia" gerrit_path="examples/fidl/fuchsia.examples/echo.test.fidl" region_tag="launcher" %} |
| ``` |
| |
| This is a protocol that lets clients retrieve an instance of the `Echo` |
| protocol. Clients can specify a prefix, and the resulting `Echo` instance |
| adds that prefix to every response. |
| |
| There are two methods that can be used to accomplish this: |
| |
| * `GetEcho`: Takes the prefix as a request, and responds with the client end of |
| a channel connected to an implementation of the `Echo` protocol. After |
| receiving the client end in the response, the client can start making requests |
| on the `Echo` protocol using the client end. |
| * `GetEchoPipelined`: Takes the server end of a channel as one of the request |
| parameters and binds an implementation of `Echo` to it. The client that |
| made the request is assumed to already hold the client end, and will |
| start making `Echo` requests on that channel after calling `GetEchoPipeliend`. |
| |
| As the name suggests, the latter uses a pattern called protocol request |
| pipelining, and is the preferred approach. This tutorial implements both |
| approaches. |
