| // Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| import 'package:json_rpc_2/json_rpc_2.dart'; |
| import 'package:web_socket_channel/web_socket_channel.dart'; |
| |
| void main() { |
| var socket = WebSocketChannel.connect(Uri.parse('ws://localhost:4321')); |
| |
| // The socket is a `StreamChannel<dynamic>` because it might emit binary |
| // `List<int>`, but JSON RPC 2 only works with Strings so we assert it only |
| // emits those by casting it. |
| var server = Server(socket.cast<String>()); |
| |
| // Any string may be used as a method name. JSON-RPC 2.0 methods are |
| // case-sensitive. |
| var i = 0; |
| server.registerMethod('count', () { |
| // Just return the value to be sent as a response to the client. This can |
| // be anything JSON-serializable, or a Future that completes to something |
| // JSON-serializable. |
| return i++; |
| }); |
| |
| // Methods can take parameters. They're presented as a `Parameters` object |
| // which makes it easy to validate that the expected parameters exist. |
| server.registerMethod('echo', (Parameters params) { |
| // If the request doesn't have a "message" parameter this will |
| // automatically send a response notifying the client that the request |
| // was invalid. |
| return params['message'].value; |
| }); |
| |
| // `Parameters` has methods for verifying argument types. |
| server.registerMethod('subtract', (Parameters params) { |
| // If "minuend" or "subtrahend" aren't numbers, this will reject the |
| // request. |
| return params['minuend'].asNum - params['subtrahend'].asNum; |
| }); |
| |
| // [Parameters] also supports optional arguments. |
| server.registerMethod('sort', (Parameters params) { |
| var list = params['list'].asList; |
| list.sort(); |
| if (params['descendint'].asBoolOr(false)) { |
| return list.reversed; |
| } else { |
| return list; |
| } |
| }); |
| |
| // A method can send an error response by throwing a `RpcException`. |
| // Any positive number may be used as an application- defined error code. |
| const dividByZero = 1; |
| server.registerMethod('divide', (Parameters params) { |
| var divisor = params['divisor'].asNum; |
| if (divisor == 0) { |
| throw RpcException(dividByZero, 'Cannot divide by zero.'); |
| } |
| |
| return params['dividend'].asNum / divisor; |
| }); |
| |
| // To give you time to register all your methods, the server won't start |
| // listening for requests until you call `listen`. Messages are buffered until |
| // listen is called. The returned Future won't complete until the connection |
| // is closed. |
| server.listen(); |
| } |