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A tiny, cross-platform, module based, MIT-licensed web server for .NET Framework and .NET Core.

• Written entirely in C#, using our helpful library SWAN
• Network operations use the async/await pattern: Responses are handled asynchronously
• Cross-platform[1]: tested in Mono on Windows and on a custom Yocto image for the Raspberry Pi
• Extensible: Write your own modules -- For example, video streaming, UPnP, etc. Check out EmbedIO Extras for additional modules.
• Small memory footprint
• Create REST APIs quickly with the out-of-the-box Web API module
• Serve static files with 1 line of code (also out-of-the-box)
• Handle sessions with the built-in LocalSessionWebModule
• WebSockets support (see notes below)
• CORS support. Origin, Header and Method validation with OPTIONS preflight
• Supports HTTP 206 Partial Content

For detailed usage and REST API implementation, download the code and take a look at the Samples project

Some usage scenarios:

• Write a cross-platform GUI entirely in CSS/HTML/JS
• Write a game using Babylon.js and make EmbedIO your serve your code and assets
• Create GUIs for Windows services or Linux daemons
• Works well with LiteLib - add SQLite support in minutes!
• Write client applications with real-time communication between them

Some notes regarding WebSocket and runtimes support:

Runtime	WebSocket support	Notes
NET46	Yes	Support Win7+ OS using a custom System.Net implementation based on Mono and websocket-sharp
NET47	Yes	Support Win8+ OS using native System.Net library
NETSTANDARD*	Yes	Support Windows, Linux and macOS using native System.Net library
UAP	No	Support Windows Universal Platform. More information here

EmbedIO before version 1.4.0 uses Newtonsoft JSON and an internal logger subsystem based on ILog interface.

NuGet Installation:

PM> Install-Package EmbedIO

Basic Example:

Please note the comments are the important part here. More info is available in the samples.

namespace Company.Project
{
    using System;
    using Unosquare.Labs.EmbedIO;
    using Unosquare.Labs.EmbedIO.Modules;

    class Program
    {
        /// <summary>
        /// Defines the entry point of the application.
        /// </summary>
        /// <param name="args">The arguments.</param>
        static void Main(string[] args)
        {
            var url = "http://localhost:9696/";
            if (args.Length > 0)
                url = args[0];

            // Our web server is disposable.
            using (var server = new WebServer(url))
            {
                // First, we will configure our web server by adding Modules.
                // Please note that order DOES matter.
                // ================================================================================================
                // If we want to enable sessions, we simply register the LocalSessionModule
                // Beware that this is an in-memory session storage mechanism so, avoid storing very large objects.
                // You can use the server.GetSession() method to get the SessionInfo object and manupulate it.
                // You could potentially implement a distributed session module using something like Redis
                server.RegisterModule(new LocalSessionModule());

                // Here we setup serving of static files
                server.RegisterModule(new StaticFilesModule("c:/web"));
                // The static files module will cache small files in ram until it detects they have been modified.
                server.Module<StaticFilesModule>().UseRamCache = true;
                server.Module<StaticFilesModule>().DefaultExtension = ".html";
                // We don't need to add the line below. The default document is always index.html.
                //server.Module<Modules.StaticFilesWebModule>().DefaultDocument = "index.html";

                // Once we've registered our modules and configured them, we call the RunAsync() method.
                server.RunAsync();

                // Fire up the browser to show the content if we are debugging!
#if DEBUG
                var browser = new System.Diagnostics.Process()
                {
                    StartInfo = new System.Diagnostics.ProcessStartInfo(url) { UseShellExecute = true }
                };
                browser.Start();
#endif
                // Wait for any key to be pressed before disposing of our web server.
                // In a service, we'd manage the lifecycle of our web server using
                // something like a BackgroundWorker or a ManualResetEvent.
                Console.ReadKey(true);
            }
        }
    }
}

Fluent Example:

Many extension methods are available. This allows you to create a web server instance in a fluent style by dotting in configuration options.

namespace Company.Project
{
    using System;
    using Unosquare.Labs.EmbedIO;

    internal class Program
    {
        /// <summary>
        /// Defines the entry point of the application.
        /// </summary>
        /// <param name="args">The arguments.</param>
        private static void Main(string[] args)
        {
            var url = "http://localhost:9696/";
            if (args.Length > 0)
                url = args[0];

            // Create Webserver and attach LocalSession and Static
            // files module and CORS enabled
            var server = WebServer
                .Create(url)
                .EnableCors()
                .WithLocalSession()
                .WithStaticFolderAt("c:/web");

            var cts = new CancellationTokenSource();
            var task = server.RunAsync(cts.Token);

            // Wait for any key to be pressed before disposing of our web server.
            // In a service, we'd manage the lifecycle of our web server using
            // something like a BackgroundWorker or a ManualResetEvent.
            Console.ReadKey(true);
            cts.Cancel();

            try
            {
                task.Wait();
            } catch (AggregateException)
            {
                // We'd also actually verify the exception cause was that the task
                // was cancelled.
                server.Dispose();
            }
        }
    }
}

REST API Example:

The WebApi module supports two routing strategies: Wildcard and Regex. By default, and in order to maintain backward compatibility, the WebApi module will use the Wildcard Routing Strategy and match routes using the asterisk * character in the route. For example:

• The route /api/people/* will match any request with a URL starting with the two first URL segments api and people and ending with anything. The route /api/people/hello will be matched.
• You can also use wildcards in the middle of the route. The route /api/people/*/details will match requests starting with the two first URL segments api and people, and end with a details segment. The route /api/people/hello/details will be matched.

Note that most REST services can be designed with this simpler Wildcard routing strategy. However, the Regex matching strategy is the current recommended approach as we might be deprecating the Wildcard strategy altogether

On the other hand, the Regex Routing Strategy will try to match and resolve the values from a route template, in a similar fashion to Microsoft's Web API 2. A method with the following route /api/people/{id} is going to match any request URL with three segments: the first two api and people and the last one is going to be parsed or converted to the type in the id argument of the handling method signature. Please read on if this was confusing as it is much simpler than it sounds. Additionally, you can put multiple values to match, for example /api/people/{mainSkill}/{age}, and receive the parsed values from the URL straight into the arguments of your handler method.

During server setup:

// The routing strategy is Wildcard by default, but you can change it to Regex as follows:
var server =  new WebServer("http://localhost:9696/", RoutingStrategy.Regex);

server.RegisterModule(new WebApiModule());
server.Module<WebApiModule>().RegisterController<PeopleController>();

And our controller class (using Regex Strategy) looks like:

public class PeopleController : WebApiController
{
    [WebApiHandler(HttpVerbs.Get, "/api/people/{id}")]
    public bool GetPeople(WebServer server, HttpListenerContext context, int id)
    {
        try
        {
            if (People.Any(p => p.Key == id))
            {
                return context.JsonResponse(People.FirstOrDefault(p => p.Key == id));
            }
        }
        catch (Exception ex)
        {
            return context.JsonExceptionResponse(ex);
        }
    }
}

Or if you want to use the Wildcard strategy (which is the default):

public class PeopleController : WebApiController
{
    [WebApiHandler(HttpVerbs.Get, "/api/people/*")]
    public bool GetPeople(WebServer server, HttpListenerContext context)
    {
        try
        {
            var lastSegment = context.Request.Url.Segments.Last();
            if (lastSegment.EndsWith("/"))
                return context.JsonResponse(People);

            int key = 0;
            if (int.TryParse(lastSegment, out key) && People.Any(p => p.Key == key))
            {
                return context.JsonResponse(People.FirstOrDefault(p => p.Key == key));
            }

            throw new KeyNotFoundException("Key Not Found: " + lastSegment);
        }
        catch (Exception ex)
        {
            return context.JsonExceptionResponse(ex);
        }
    }
}

WebSockets Example:

During server setup:

server.RegisterModule(new WebSocketsModule());
server.Module<WebSocketsModule>().RegisterWebSocketsServer<WebSocketsChatServer>("/chat");

And our web sockets server class looks like:

/// <summary>
/// Defines a very simple chat server
/// </summary>
public class WebSocketsChatServer : WebSocketsServer
{
    public WebSocketsChatServer()
        : base(true, 0)
    {
        // placeholder
    }

    /// <summary>
    /// Called when this WebSockets Server receives a full message (EndOfMessage) form a WebSockets client.
    /// </summary>
    /// <param name="context">The context.</param>
    /// <param name="rxBuffer">The rx buffer.</param>
    /// <param name="rxResult">The rx result.</param>
    protected override void OnMessageReceived(WebSocketContext context, byte[] rxBuffer, WebSocketReceiveResult rxResult)
    {
        var session = this.WebServer.GetSession(context);
        foreach (var ws in this.WebSockets)
        {
            if (ws != context)
                this.Send(ws, rxBuffer.ToText());
        }
    }

    /// <inheritdoc/>
    public override string ServerName => "Chat Server"

    /// <summary>
    /// Called when this WebSockets Server accepts a new WebSockets client.
    /// </summary>
    /// <param name="context">The context.</param>
    protected override void OnClientConnected(WebSocketContext context)
    {
        this.Send(context, "Welcome to the chat room!");
        
        foreach (var ws in this.WebSockets)
        {
            if (ws != context)
                this.Send(ws, "Someone joined the chat room.");
        }
    }

    /// <summary>
    /// Called when this WebSockets Server receives a message frame regardless if the frame represents the EndOfMessage.
    /// </summary>
    /// <param name="context">The context.</param>
    /// <param name="rxBuffer">The rx buffer.</param>
    /// <param name="rxResult">The rx result.</param>
    protected override void OnFrameReceived(WebSocketContext context, byte[] rxBuffer, WebSocketReceiveResult rxResult)
    {
        return;
    }

    /// <summary>
    /// Called when the server has removed a WebSockets connected client for any reason.
    /// </summary>
    /// <param name="context">The context.</param>
    protected override void OnClientDisconnected(WebSocketContext context)
    {
        this.Broadcast("Someone left the chat room.");
    }
}

Notes

[1] - EmbedIO uses lowercase URL parts. In Windows systems, this is the expected behavior but in Unix systems using MONO please refer to Mono IOMap if you want to work with case-insensitive URL parts.