signalr_client
A Flutter SignalR Client for ASP.NET Core.
ASP.NET Core SignalR is an open-source library that simplifies adding real-time web functionality to apps. Real-time web functionality enables server-side code to push content to clients instantly.
Tested with ASP.NET Core 3.1 & ASP .NET Core 6
The client is able to invoke server side hub functions (including streaming functions) and to receive method invocations issued by the server. It also supports the auto-reconnect feature.
The client supports the following transport protocols:
- WebSocket
- Service Side Events
- Long Polling
The client supports the following hub protocols:
- Json
- MessagePack
Examples
- Chat client/server - A simple client/server chat application.
- Integration test app - To see how a client calls various types of hub functions.
Getting Started
Add signalr_netcore to your pubspec.yaml dependencies:
...
dependencies:
flutter:
sdk: flutter
signalr_netcore:
...Important Note: if you are experiencing issues (for example not receiving message callback) with the latest version, please give a try to older version as signalr_netcore: 0.1.7+2-nullsafety.3 but bear in mind that this version does not support auto reconnect functionalities and need to be handled manually.
Usage
Let's demo some basic usages:
1. Create a hub connection:
// Import the library.
import 'package:signalr_netcore/signalr_client.dart';
// The location of the SignalR Server.
final serverUrl = "192.168.10.50:51001";
// Creates the connection by using the HubConnectionBuilder.
final hubConnection = HubConnectionBuilder().withUrl(serverUrl).build();
// When the connection is closed, print out a message to the console.
final hubConnection.onclose( (error) => print("Connection Closed"));
Logging is supported via the dart logging package:
// Import theses libraries.
import 'package:logging/logging.dart';
import 'package:signalr_netcore/signalr_client.dart';
// Configer the logging
Logger.root.level = Level.ALL;
// Writes the log messages to the console
Logger.root.onRecord.listen((LogRecord rec) {
print('${rec.level.name}: ${rec.time}: ${rec.message}');
});
// If you want only to log out the message for the higer level hub protocol:
final hubProtLogger = Logger("SignalR - hub");
// If youn want to also to log out transport messages:
final transportProtLogger = Logger("SignalR - transport");
// The location of the SignalR Server.
final serverUrl = "192.168.10.50:51001";
final connectionOptions = HttpConnectionOptions
final httpOptions = new HttpConnectionOptions(logger: transportProtLogger);
//final httpOptions = new HttpConnectionOptions(logger: transportProtLogger, transport: HttpTransportType.WebSockets); // default transport type.
//final httpOptions = new HttpConnectionOptions(logger: transportProtLogger, transport: HttpTransportType.ServerSentEvents);
//final httpOptions = new HttpConnectionOptions(logger: transportProtLogger, transport: HttpTransportType.LongPolling);
// If you need to authorize the Hub connection than provide a an async callback function that returns
// the token string (see AccessTokenFactory typdef) and assigned it to the accessTokenFactory parameter:
// final httpOptions = new HttpConnectionOptions( .... accessTokenFactory: () async => await getAccessToken() );
// Creates the connection by using the HubConnectionBuilder.
final hubConnection = HubConnectionBuilder().withUrl(serverUrl, options: httpOptions).configureLogging(hubProtLogger).build();
// When the connection is closed, print out a message to the console.
final hubConnection.onclose( (error) => print("Connection Closed"));
2. Connect to a Hub:
Calling following method starts handshaking and connects the client to SignalR server
await hubConnection.start();3. Calling a Hub function:
Assuming there is this hub function:
public string MethodOneSimpleParameterSimpleReturnValue(string p1)
{
Console.WriteLine($"'MethodOneSimpleParameterSimpleReturnValue' invoked. Parameter value: '{p1}");
return p1;
}The client can invoke the function by using:
final result = await hubConnection.invoke("MethodOneSimpleParameterSimpleReturnValue", args: <Object>["ParameterValue"]);
logger.log(LogLevel.Information, "Result: '$result");
4. Calling a client function:
Assuming the server calls a function "aClientProvidedFunction":
await Clients.Caller.SendAsync("aClientProvidedFunction", null);The Client provides the function like this:
hubConnection.on("aClientProvidedFunction", _handleAClientProvidedFunction);
// To unregister the function use:
// a) to unregister a specific implementation:
// hubConnection.off("aClientProvidedFunction", method: _handleServerInvokeMethodNoParametersNoReturnValue);
// b) to unregister all implementations:
// hubConnection.off("aClientProvidedFunction");
...
void _handleAClientProvidedFunction(List<Object> parameters) {
logger.log(LogLevel.Information, "Server invoked the method");
}
5. Using Msgpack for serialization
The Hub should be configured to use the msgpack protocol in both the client and server
Client
import 'package:signalr_netcore/msgpack_hub_protocol.dart';
_hubConnection = HubConnectionBuilder()
.withUrl(_serverUrl, options: httpOptions)
/* Configure the Hub with msgpack protocol */
.withHubProtocol(MessagePackHubProtocol())
.withAutomaticReconnect()
.configureLogging(logger)
.build();Server
Add the following packge to your ASP NET core project
Microsoft.AspNetCore.SignalR.Protocols.MessagePack
public void ConfigureServices(IServiceCollection services)
{
// Configure the hub to use msgpack protocol
services.AddSignalR().AddMessagePackProtocol();
}A note about the parameter types
All function parameters and return values are serialized/deserialized into/from JSON by using the dart:convert package (json.endcode/json.decode). Make sure that you:
- use only simple parameter types
or
- use objects that implements toJson() since that method is used by the dart:convert package to serialize an object.
Flutter Json 101:
MSGPACK
All function parameters and return values are serialized/deserialized into/from Msgpack by using the msgpack_dart package. Make sure that you:
- use only simple parameter types or
- Convert your classes to maps using Json encode/decode and then pass it to msgpack or
- Serialize the message into bytes using msgpack_dart using custom encoders and decoders before passing it to signalr
Msgpack - It's like JSON but fast and small.
How to expose a MessageHeaders object so the client can send default headers
Code Example:
final defaultHeaders = MessageHeaders();
defaultHeaders.setHeaderValue("HEADER_MOCK_1", "HEADER_VALUE_1");
defaultHeaders.setHeaderValue("HEADER_MOCK_2", "HEADER_VALUE_2");
final httpConnectionOptions = new HttpConnectionOptions(
httpClient: WebSupportingHttpClient(logger,
httpClientCreateCallback: _httpClientCreateCallback),
accessTokenFactory: () => Future.value('JWT_TOKEN'),
logger: logger,
logMessageContent: true,
headers: defaultHeaders);
final _hubConnection = HubConnectionBuilder()
.withUrl(_serverUrl, options: httpConnectionOptions)
.withAutomaticReconnect(retryDelays: [2000, 5000, 10000, 20000, null])
.configureLogging(logger)
.build();Http Request Log:
I/flutter ( 5248): Starting connection with transfer format 'TransferFormat.Text'.
I/flutter ( 5248): Sending negotiation request: https://localhost:5000/negotiate?negotiateVersion=1
I/flutter ( 5248): HTTP send: url 'https://localhost:5000/negotiate?negotiateVersion=1', method: 'POST' content: '' content length = '0'
headers: '{ content-type: text/plain;charset=UTF-8 }, { HEADER_MOCK_1: HEADER_VALUE_1 }, { X-Requested-With: FlutterHttpClient }, { HEADER_MOCK_2: HEADER_VALUE_2 }, { Authorization: Bearer JWT_TOKEN }'
