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101 lines
3.4 KiB
101 lines
3.4 KiB
---
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sidebar_position: 1
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title: Websocket
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---
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This course explains how to get started with WebSockets in ASP.NET Core.
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[WebSocket](https://wikipedia.org/wiki/WebSocket) ([RFC 6455](https://tools.ietf.org/html/rfc6455)) is a protocol that allows persistent two-way communication channels over TCP connections.
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Its use benefits applications that take advantage of fast, real-time communication, such as chat, dashboard, and game applications.
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For our examples we will use a small example project available [here](/DemoWebsocket.zip).
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## WebSocket definition
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In the traditional web paradigm, the client was responsible for initiating communication with a server, and the server could not send data back unless it had been previously requested by the client.
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With WebSockets, you can send data between server and client over a single TCP connection, and typically WebSockets are used to provide real-time functionality to modern applications.
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## What is a SignalR Hub?
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The SignalR hubs API lets you call methods on connected clients from the server.
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* In server code, you define methods that are called by the client.
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* In client code, you define methods that are called from the server.
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SignalR takes care of everything in the background that makes real-time client-to-server and server-to-client communications possible.
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## Install the SignalR .NET client package
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The `Microsoft.AspNetCore.SignalR.Client` package is required for .NET clients to connect to SignalR hubs.
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Install the `Microsoft.AspNetCore.SignalR.Client` package in its latest version.
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Or using the Package Manager console: `PM> Install-Package Microsoft.AspNetCore.SignalR.Client`
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## Use SignalR
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To establish a connection, create a `HubConnectionBuilder` and call the `Build` method.
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Hub URL, protocol, transport type, logging level, headers, and other options can be configured when creating a connection.
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Configure all required options by inserting one of the `HubConnectionBuilder` methods into the `Build` method.
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Start the connection with `StartAsync`.
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```csharp title="DemoSignalR.razor.cs"
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public partial class DemoSignalR
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{
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private HubConnection connection;
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private string connectionUrl = "https://localhost:44391/ChatHub";
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private List<Chat> logs = new List<Chat>();
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private string message = "";
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private string userName = "UserName";
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public DemoSignalR()
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{
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// Create the new SignalR Hub
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connection = new HubConnectionBuilder()
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.WithUrl(connectionUrl)
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.Build();
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}
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public void Dispose()
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{
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OnClose();
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}
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private async void OnClose()
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{
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// Send message for user disconnect
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await connection.InvokeAsync("SendMessage", new Chat { Type = "disconnect", Name = userName });
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// Stop the connection
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await connection.StopAsync();
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}
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private async void OnConnect()
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{
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// Handler to treat the receive message
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connection.On<Chat>("ReceiveMessage", chat =>
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{
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logs.Add(chat);
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StateHasChanged();
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});
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// Start the connection
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await connection.StartAsync();
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// Send message for user connect
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await connection.InvokeAsync("SendMessage", new Chat { Type = "connect", Name = userName });
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}
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private async Task SendMessageAsync()
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{
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// Send the user message
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await connection.InvokeAsync("SendMessage", new Chat { Type = "message", Name = userName, Message = message });
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}
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}
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```
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