What is SignalR?

In this post, we will explore the answers to the questions “What is SignalR?” and “Why is it used?”. SignalR is a library for real-time web applications. This library provides a socket connection between the web server and the client, enabling real-time communication between them. SignalR is a library that works with JavaScript, .NET, and ASP.NET.

SignalR offers several methods to facilitate messaging between the server and the client. These methods include WebSocket, Server-Sent Events (SSE), and Long Polling. SignalR uses protocols such as WebSocket and SSE to deliver real-time data in browsers that support these technologies. For other browsers, it uses Long Polling for data transmission.

SignalR can send messages to multiple clients simultaneously. These messages can be sent to all clients connected to the server at the same time.

How to Use SignalR?

To use SignalR, you first need to create a server-side and a client-side. On the server side, you need to configure SignalR and create a custom hub class to handle messages. On the client side, you must create a SignalR client and connect it to the server-side hub class.

To configure SignalR on the server side, you can add the following code to the Startup.cs file:

public void ConfigureServices(IServiceCollection services)
{
    services.AddSignalR();
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    app.UseRouting();

    app.UseEndpoints(endpoints =>
    {
        endpoints.MapHub<MyHub>;("/myhub");
    });
}

This code adds the necessary services and the hub required to configure SignalR.

You can use the following code to create a hub class:

public class MyHub : Hub
{
    public async Task SendMessage(string user, string message)
    {
        await Clients.All.SendAsync("ReceiveMessage", user, message);
    }
}

This code creates a method called SendMessage. This method takes the parameters user and message and sends them to all clients by invoking a method named ReceiveMessage.

On the client side, you can add the following code to use the SignalR client:

var connection = new signalR.HubConnectionBuilder().withUrl("/myhub").build();

connection.on("ReceiveMessage", function (user, message) {
    // message handling logic here
});

connection.start().then(function () {
    connection.invoke("SendMessage", user, message).catch(function (err) {
        console.error(err.toString());
    });
}).catch(function (err) {
    console.error(err.toString());
});

This code uses the HubConnectionBuilder class to configure the SignalR client. The connection.on method is used to handle messages received from the server. The connection.start method establishes a connection between the client and the server. The connection.invoke method is used to send messages to the server.

SignalR, being a powerful library, can be used for real-time web applications. By leveraging SignalR, web applications can become more interactive and user-friendly by facilitating real-time communication between the server and the client. SignalR supports technologies such as WebSocket, SSE, and Long Polling for real-time data transmission. This enables improved performance and enhanced user experience.

For detailed information, you can access the Microsoft documentation here.