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.

The client is able to invoke server side hub functions (including streaming functions) and to receive method invocations issued by the server.

The client supports the following transport protocols:

• WebSocket
• Service Side Events
• Long Polling

The client supports the following hub protocols:

• Json
• MessagePack - Since I can't find a MessagePack library that support the current flutter version.

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_client to your pubspec.yaml dependencies:

...
dependencies:
  flutter:
    sdk: flutter

  signalr_client:
...

Usage

Let's demo some basic usages:

1. Create a hub connection:

// Import the library.
import 'package:signalr_client/signalr_client.dart';

// The location of the SignalR Server.
final serverUrl = "192.168.10.50:51001";
// Prints log messages to the console.
final logger = ConsoleLogger();
// Creates the connection by using the HubConnectionBuilder.
final hubConnection = HubConnectionBuilder().withUrl(serverUrl).configureLogging(logger: logger).build();
// When the connection is closed, print out a message to the logger.
final hubConnection.onclose( (error) => logger.log(LogLevel.Information, "Connection Closed"));

2. 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");

3. 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");
  }

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:

• flutter.io
• json.encode
• json.decode