HttpListener based SSE Server Support (#73)

tests/mcpdotnet.Tests/Configuration/McpServerBuilderExtensionsTransportsTests.cs

@@ -20,4 +20,18 @@ public class McpServerBuilderExtensionsTransportsTests
         Assert.NotNull(transportType);
         Assert.Equal(typeof(StdioServerTransport), transportType.ImplementationType);
     }
+
+    [Fact]
+    public void WithHttpListenerSseServerTransport_Sets_Transport()
+    {
+        var services = new ServiceCollection();
+        var builder = new Mock<IMcpServerBuilder>();
+        builder.SetupGet(b => b.Services).Returns(services);
+
+        builder.Object.WithHttpListenerSseServerTransport();
+
+        var transportType = services.FirstOrDefault(s => s.ServiceType == typeof(IServerTransport));
+        Assert.NotNull(transportType);
+        Assert.Equal(typeof(HttpListenerSseServerTransport), transportType.ImplementationType);
+    }
 }

tests/mcpdotnet.Tests/SseIntegrationTests.cs

@@ -18,7 +18,7 @@ public class SseIntegrationTests
             builder.AddConsole()
             .SetMinimumLevel(LogLevel.Debug));
 
-        await using TestSseServer server = new(logger: loggerFactory.CreateLogger<TestSseServer>());
+        await using InMemoryTestSseServer server = new(logger: loggerFactory.CreateLogger<InMemoryTestSseServer>());
         await server.StartAsync();
 
 
@@ -164,7 +164,7 @@ public class SseIntegrationTests
             builder.AddConsole()
             .SetMinimumLevel(LogLevel.Debug));
 
-        await using TestSseServer server = new(logger: loggerFactory.CreateLogger<TestSseServer>());
+        await using InMemoryTestSseServer server = new(logger: loggerFactory.CreateLogger<InMemoryTestSseServer>());
         server.UseFullUrlForEndpointEvent = true;
         await server.StartAsync();
 
@@ -204,7 +204,7 @@ public class SseIntegrationTests
             builder.AddConsole()
             .SetMinimumLevel(LogLevel.Debug));
 
-        await using TestSseServer server = new(logger: loggerFactory.CreateLogger<TestSseServer>());
+        await using InMemoryTestSseServer server = new(logger: loggerFactory.CreateLogger<InMemoryTestSseServer>());
         await server.StartAsync();
 
 
@@ -253,7 +253,7 @@ public class SseIntegrationTests
             builder.AddConsole()
             .SetMinimumLevel(LogLevel.Debug));
 
-        await using TestSseServer server = new(logger: loggerFactory.CreateLogger<TestSseServer>());
+        await using InMemoryTestSseServer server = new(logger: loggerFactory.CreateLogger<InMemoryTestSseServer>());
         await server.StartAsync();
 
 

tests/mcpdotnet.Tests/SseServerIntegrationTestFixture.cs

@@ -0,0 +1,83 @@
+using McpDotNet.Client;
+using McpDotNet.Configuration;
+using McpDotNet.Protocol.Transport;
+using Microsoft.Extensions.Logging;
+using System.Diagnostics;
+
+namespace McpDotNet.Tests;
+
+public class SseServerIntegrationTestFixture : IDisposable
+{
+    private Process _process;
+
+    public ILoggerFactory LoggerFactory { get; }
+    public McpClientFactory Factory { get; }
+    public McpClientOptions DefaultOptions { get; }
+    public McpServerConfig DefaultConfig { get; }
+
+    public SseServerIntegrationTestFixture()
+    {
+        LoggerFactory = Microsoft.Extensions.Logging.LoggerFactory.Create(builder =>
+            builder.AddConsole()
+            .SetMinimumLevel(LogLevel.Debug));
+
+        DefaultOptions = new()
+        {
+            ClientInfo = new() { Name = "IntegrationTestClient", Version = "1.0.0" },
+            Capabilities = new() { Sampling = new(), Roots = new() }
+        };
+
+        DefaultConfig = new McpServerConfig
+        {
+            Id = "test_server",
+            Name = "TestServer",
+            TransportType = TransportTypes.Sse,
+            TransportOptions = [],
+            Location = "http://localhost:3001/sse"
+        };
+
+        // Inject the mock transport into the factory
+        Factory = new McpClientFactory(
+            [DefaultConfig],
+            DefaultOptions,
+            LoggerFactory
+        );
+
+        Start();
+    }
+
+    public void Start()
+    {
+        // Start the server (which is at TestSseServer.exe on windows and "dotnet TestSseServer.dll" on linux)
+        var processStartInfo = new ProcessStartInfo
+        {
+            FileName = OperatingSystem.IsWindows() ? "TestSseServer.exe" : "dotnet",
+            Arguments = "TestSseServer.dll",
+            RedirectStandardInput = true,
+            RedirectStandardOutput = true,
+            RedirectStandardError = true,
+            UseShellExecute = false,
+        };
+
+        _process = Process.Start(processStartInfo)
+            ?? throw new InvalidOperationException($"Could not start process for {processStartInfo.FileName} with '{processStartInfo.Arguments}'.");
+
+        // Wait 1 second
+        Thread.Sleep(1000);
+    }
+
+    public void Dispose()
+    {
+        try
+        {
+            var client = Factory.GetClientAsync("test_server").Result;
+            client.DisposeAsync().AsTask().Wait();
+            LoggerFactory?.Dispose();
+        }
+        finally
+        {
+            // Kill the server process
+            _process.Kill();
+        }
+    }
+}

tests/mcpdotnet.Tests/SseServerIntegrationTests.cs

@@ -0,0 +1,235 @@
+using McpDotNet.Client;
+using McpDotNet.Protocol.Types;
+
+namespace McpDotNet.Tests;
+
+public class SseServerIntegrationTests : IClassFixture<SseServerIntegrationTestFixture>
+{
+    private readonly SseServerIntegrationTestFixture _fixture;
+
+    public SseServerIntegrationTests(SseServerIntegrationTestFixture fixture)
+    {
+        _fixture = fixture;
+    }
+
+    [Fact]
+    public async Task ConnectAndPing_Sse_TestServer()
+    {
+        // Arrange
+
+        // Act
+        var client = await _fixture.Factory.GetClientAsync("test_server");
+        await client.PingAsync(CancellationToken.None);
+
+        // Assert
+        Assert.NotNull(client);
+    }
+
+    [Fact]
+    public async Task Connect_TestServer_ShouldProvideServerFields()
+    {
+        // Arrange
+
+        // Act
+        var client = await _fixture.Factory.GetClientAsync("test_server");
+
+        // Assert
+        Assert.NotNull(client.ServerCapabilities);
+        Assert.NotNull(client.ServerInfo);
+    }
+
+    [Fact]
+    public async Task ListTools_Sse_TestServer()
+    {        
+        // arrange
+
+        // act
+        var client = await _fixture.Factory.GetClientAsync("test_server");
+        var tools = await client.ListToolsAsync().ToListAsync();
+
+        // assert
+        Assert.NotNull(tools);
+    }
+
+    [Fact]
+    public async Task CallTool_Sse_EchoServer()
+    {
+        // arrange
+
+        // act
+        var client = await _fixture.Factory.GetClientAsync("test_server");
+        var result = await client.CallToolAsync(
+            "echo",
+            new Dictionary<string, object>
+            {
+                ["message"] = "Hello MCP!"
+            },
+            CancellationToken.None
+        );
+
+        // assert
+        Assert.NotNull(result);
+        Assert.False(result.IsError);
+        var textContent = Assert.Single(result.Content, c => c.Type == "text");
+        Assert.Equal("Echo: Hello MCP!", textContent.Text);
+    }
+
+    [Fact]
+    public async Task ListResources_Sse_TestServer()
+    {
+        // arrange
+
+        // act
+        var client = await _fixture.Factory.GetClientAsync("test_server");
+
+        List<Resource> allResources = [];
+        string? cursor = null;
+        do
+        {
+            var resources = await client.ListResourcesAsync(cursor, CancellationToken.None);
+            allResources.AddRange(resources.Resources);
+            cursor = resources.NextCursor;
+        }
+        while (cursor != null);
+
+        // The everything server provides 100 test resources
+        Assert.Equal(100, allResources.Count);
+    }
+
+    [Fact]
+    public async Task ReadResource_Sse_TextResource()
+    {
+        // arrange
+
+        // act
+        var client = await _fixture.Factory.GetClientAsync("test_server");
+        // Odd numbered resources are text in the everything server (despite the docs saying otherwise)
+        // 1 is index 0, which is "even" in the 0-based index
+        // We copied this oddity to the test server
+        var result = await client.ReadResourceAsync("test://static/resource/1", CancellationToken.None);
+
+        Assert.NotNull(result);
+        Assert.Single(result.Contents);
+        Assert.NotNull(result.Contents[0].Text);
+    }
+
+    [Fact]
+    public async Task ReadResource_Sse_BinaryResource()
+    {
+        // arrange
+
+        // act
+        var client = await _fixture.Factory.GetClientAsync("test_server");
+        // Even numbered resources are binary in the everything server (despite the docs saying otherwise)
+        // 2 is index 1, which is "odd" in the 0-based index
+        // We copied this oddity to the test server
+        var result = await client.ReadResourceAsync("test://static/resource/2", CancellationToken.None);
+
+        Assert.NotNull(result);
+        Assert.Single(result.Contents);
+        Assert.NotNull(result.Contents[0].Blob);
+    }
+
+    [Fact]
+    public async Task ListPrompts_Sse_TestServer()
+    {
+        // arrange
+
+        // act
+        var client = await _fixture.Factory.GetClientAsync("test_server");
+        var prompts = await client.ListPromptsAsync().ToListAsync();
+
+        // assert
+        Assert.NotNull(prompts);
+        Assert.NotEmpty(prompts);
+        // We could add specific assertions for the known prompts
+        Assert.Contains(prompts, p => p.Name == "simple_prompt");
+        Assert.Contains(prompts, p => p.Name == "complex_prompt");
+    }
+
+    [Fact]
+    public async Task GetPrompt_Sse_SimplePrompt()
+    {
+        // arrange
+
+        // act
+        var client = await _fixture.Factory.GetClientAsync("test_server");
+        var result = await client.GetPromptAsync("simple_prompt", null, CancellationToken.None);
+
+        // assert
+        Assert.NotNull(result);
+        Assert.NotEmpty(result.Messages);
+    }
+
+    [Fact]
+    public async Task GetPrompt_Sse_ComplexPrompt()
+    {
+        // arrange
+
+        // act
+        var client = await _fixture.Factory.GetClientAsync("test_server");
+        var arguments = new Dictionary<string, object>
+        {
+            { "temperature", "0.7" },
+            { "style", "formal" }
+        };
+        var result = await client.GetPromptAsync("complex_prompt", arguments, CancellationToken.None);
+
+        // assert
+        Assert.NotNull(result);
+        Assert.NotEmpty(result.Messages);
+    }
+
+    [Fact]
+    public async Task GetPrompt_Sse_NonExistent_ThrowsException()
+    {
+        // arrange
+
+        // act
+        var client = await _fixture.Factory.GetClientAsync("test_server");
+        await Assert.ThrowsAsync<McpClientException>(() =>
+            client.GetPromptAsync("non_existent_prompt", null, CancellationToken.None));
+    }
+
+    [Fact]
+    public async Task Sampling_Sse_TestServer()
+    {
+        // arrange        
+        var client = await _fixture.Factory.GetClientAsync("test_server");
+
+        // Set up the sampling handler
+        int samplingHandlerCalls = 0;
+#pragma warning disable CS1998 // Async method lacks 'await' operators and will run synchronously
+        client.SetSamplingHandler(async (_, _) =>
+        {
+            samplingHandlerCalls++;
+            return new CreateMessageResult
+            {
+                Model = "test-model",
+                Role = "assistant",
+                Content = new Content
+                {
+                    Type = "text",
+                    Text = "Test response"
+                }
+            };
+        });
+#pragma warning restore CS1998 // Async method lacks 'await' operators and will run synchronously
+
+        // Call the server's sampleLLM tool which should trigger our sampling handler
+        var result = await client.CallToolAsync(
+            "sampleLLM",
+            new Dictionary<string, object>
+            {
+                ["prompt"] = "Test prompt",
+                ["maxTokens"] = 100
+            }
+        );
+
+        // assert
+        Assert.NotNull(result);
+        var textContent = Assert.Single(result.Content);
+        Assert.Equal("text", textContent.Type);
+        Assert.False(string.IsNullOrEmpty(textContent.Text));
+    }
+}

tests/mcpdotnet.Tests/Utils/InMemoryTestSseServer.cs

@@ -0,0 +1,382 @@
+using System.Collections.Concurrent;
+using System.Net;
+using System.Text.Json;
+using McpDotNet.Protocol.Messages;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
+
+namespace McpDotNet.Tests.Utils;
+
+public sealed class InMemoryTestSseServer : IAsyncDisposable
+{
+    private readonly HttpListener _listener;
+    private readonly CancellationTokenSource _cts;
+    private readonly ILogger<InMemoryTestSseServer> _logger;
+    private Task? _serverTask;
+    private readonly TaskCompletionSource _connectionEstablished = new();
+
+    // SSE endpoint for GET
+    private readonly string _endpointPath;
+    // POST endpoint
+    private readonly string _messagePath;
+
+    // Keep track of all open SSE connections (StreamWriters).
+    private readonly ConcurrentBag<StreamWriter> _sseClients = [];
+
+    public InMemoryTestSseServer(int port = 5000, ILogger<InMemoryTestSseServer>? logger = null)
+    {
+        _listener = new HttpListener();
+        _listener.Prefixes.Add($"http://localhost:{port}/");
+        _cts = new CancellationTokenSource();
+        _logger = logger ?? NullLogger<InMemoryTestSseServer>.Instance;
+
+        _endpointPath = "/sse";
+        _messagePath = "/message";
+    }
+
+    /// <summary>
+    /// This is to be able to use the full URL for the endpoint event.
+    /// </summary>
+    public bool UseFullUrlForEndpointEvent { get; set; }
+
+    /// <summary>
+    /// Full URL for the SSE endpoint, e.g. "http://localhost:5000/sse"
+    /// </summary>
+    public string SseEndpoint
+        => $"http://localhost:{_listener.Prefixes.First().Split(':')[2].TrimEnd('/')}{_endpointPath}";
+
+    /// <summary>
+    /// Full URL for the message endpoint, e.g. "http://localhost:5000/message"
+    /// </summary>
+    public string MessageEndpoint
+        => $"http://localhost:{_listener.Prefixes.First().Split(':')[2].TrimEnd('/')}{_messagePath}";
+
+    /// <summary>
+    /// Starts the server so it can accept incoming connections and POST requests.
+    /// </summary>
+    public async Task StartAsync()
+    {
+        _listener.Start();
+        _serverTask = HandleConnectionsAsync(_cts.Token);
+
+        _logger.LogInformation("Test SSE server started on {Endpoint}", SseEndpoint);
+        await Task.CompletedTask;
+    }
+
+    private async Task HandleConnectionsAsync(CancellationToken ct)
+    {
+        try
+        {
+            while (!ct.IsCancellationRequested)
+            {
+                var context = await _listener.GetContextAsync();
+                _ = Task.Run(() => HandleRequestAsync(context, ct), ct);
+            }
+        }
+        catch (OperationCanceledException)
+        {
+            // Ignore, we are shutting down
+        }
+        catch (Exception ex) when (!ct.IsCancellationRequested)
+        {
+            _logger.LogError(ex, "Error in SSE server connection handling");
+        }
+    }
+
+    private async Task HandleRequestAsync(HttpListenerContext context, CancellationToken ct)
+    {
+        var request = context.Request;
+        var response = context.Response;
+
+        // Handle SSE endpoint
+        if (request.HttpMethod.Equals("GET", StringComparison.OrdinalIgnoreCase)
+            && request.Url?.AbsolutePath.Equals(_endpointPath, StringComparison.OrdinalIgnoreCase) == true)
+        {
+            await HandleSseConnectionAsync(context, ct);
+        }
+        // Handle POST /message
+        else if (request.HttpMethod.Equals("POST", StringComparison.OrdinalIgnoreCase)
+                 && request.Url?.AbsolutePath.Equals(_messagePath, StringComparison.OrdinalIgnoreCase) == true)
+        {
+            await HandlePostMessageAsync(context, ct);
+        }
+        else
+        {
+            response.StatusCode = 404;
+            response.Close();
+        }
+    }
+
+    /// <summary>
+    /// Handle Server-Sent Events (SSE) connection.
+    /// Send the initial event: endpoint with the full POST URL.
+    /// Keep the connection open until the server is disposed or the client disconnects.
+    /// </summary>
+    private async Task HandleSseConnectionAsync(HttpListenerContext context, CancellationToken ct)
+    {
+        var response = context.Response;
+        response.ContentType = "text/event-stream";
+        response.Headers["Cache-Control"] = "no-cache";
+        // Ensures the response is never chunked away by the framework
+        response.SendChunked = true;
+        response.StatusCode = (int)HttpStatusCode.OK;
+
+        using var writer = new StreamWriter(response.OutputStream);
+        _sseClients.Add(writer);
+
+        // Immediately send the "endpoint" event with the POST URL
+        await writer.WriteLineAsync("event: endpoint");
+        if (UseFullUrlForEndpointEvent)
+        {
+            await writer.WriteLineAsync($"data: {MessageEndpoint}");
+        }
+        else
+        {
+            await writer.WriteLineAsync($"data: {_messagePath}");
+        }
+        await writer.WriteLineAsync(); // blank line to end an SSE message
+        await writer.FlushAsync(ct);
+
+        _logger.LogInformation("New SSE client connected.");
+        _connectionEstablished.TrySetResult(); // Signal connection is ready
+
+        try
+        {
+            // Keep the connection open by "pinging" or just waiting
+            // until the client disconnects or the server is canceled.
+            while (!ct.IsCancellationRequested && response.OutputStream.CanWrite)
+            {
+                _logger.LogDebug("SSE connection alive check");
+                // Optionally do a periodic no-op to keep connection alive:
+                await writer.WriteLineAsync(": keep-alive");
+                await writer.FlushAsync(ct);
+                await Task.Delay(TimeSpan.FromSeconds(5), ct);
+            }
+        }
+        catch (TaskCanceledException)
+        {
+            // This is expected on shutdown
+            _logger.LogInformation("SSE connection cancelled (expected on shutdown)");
+        }
+        catch (IOException)
+        {
+            // Client likely disconnected
+            _logger.LogInformation("SSE client disconnected");
+        }
+        finally
+        {
+            // Remove this writer from bag (we're disposing it anyway)
+            _sseClients.TryTake(out _);
+            _logger.LogInformation("SSE client disconnected.");
+        }
+    }
+
+    // Add method to wait for connection
+    public Task WaitForConnectionAsync(TimeSpan timeout) =>
+        _connectionEstablished.Task.WaitAsync(timeout);
+
+    /// <summary>
+    /// Handle POST /message endpoint.
+    /// Echo the content back to the caller and broadcast it over SSE as well.
+    /// </summary>
+    private async Task HandlePostMessageAsync(HttpListenerContext context, CancellationToken cancellationToken)
+    {
+        var request = context.Request;
+        var response = context.Response;
+
+        try
+        {
+            using var reader = new StreamReader(request.InputStream);
+            string content = await reader.ReadToEndAsync(cancellationToken);
+
+            var jsonRpcNotification = JsonSerializer.Deserialize<JsonRpcNotification>(content);
+            if (jsonRpcNotification != null && jsonRpcNotification.Method != "initialize")
+            {
+                // Test server so just ignore notifications
+
+                // Set status code to 202 Accepted
+                response.StatusCode = 202;
+
+                // Write "accepted" as the response body
+                using var writer = new StreamWriter(response.OutputStream);
+                await writer.WriteAsync("accepted");
+                await writer.FlushAsync(cancellationToken);
+                return;
+            }
+
+            var jsonRpcRequest = JsonSerializer.Deserialize<JsonRpcRequest>(content);
+
+            if (jsonRpcRequest != null)
+            {
+                if (jsonRpcRequest.Method == "initialize")
+                {
+                    await HandleInitializationRequest(response, jsonRpcRequest);
+                }
+                else
+                {
+                    // Set status code to 202 Accepted
+                    response.StatusCode = 202;
+
+                    // Write "accepted" as the response body
+                    using var writer = new StreamWriter(response.OutputStream);
+                    await writer.WriteAsync("accepted");
+                    await writer.FlushAsync(cancellationToken);
+
+                    // Then process the message and send the response via SSE
+                    if (jsonRpcRequest != null)
+                    {
+                        // Process the request and generate a response
+                        var responseMessage = await ProcessRequestAsync(jsonRpcRequest);
+
+                        // Send the response via the SSE connection instead of HTTP response
+                        await SendSseMessageAsync(responseMessage);
+                    }
+                }
+            }
+        }
+        catch (Exception ex)
+        {
+            await SendJsonRpcErrorAsync(response, null, -32603, "Internal error", ex.Message);
+            response.StatusCode = 500;
+        }
+        finally
+        {
+            response.Close();
+        }
+    }
+
+    private static Task<JsonRpcResponse> ProcessRequestAsync(JsonRpcRequest jsonRpcRequest)
+    {
+        // This is a test server so we just echo back the request
+        return Task.FromResult(new JsonRpcResponse
+        {
+            Id = jsonRpcRequest.Id,
+            Result = jsonRpcRequest.Params!
+        });
+    }
+
+    private async Task SendSseMessageAsync(JsonRpcResponse jsonRpcResponse)
+    {
+        // This is a test server so we just send to all connected clients
+        await BroadcastMessageAsync(JsonSerializer.Serialize(jsonRpcResponse));
+    }
+
+    private static async Task SendJsonRpcErrorAsync(HttpListenerResponse response, RequestId? id, int code, string message, string? data = null)
+    {
+        var errorResponse = new JsonRpcError
+        {
+            Id = id ?? RequestId.FromString("error"),
+            JsonRpc = "2.0",
+            Error = new JsonRpcErrorDetail
+            {
+                Code = code,
+                Message = message,
+                Data = data
+            }
+        };
+
+        response.StatusCode = 200; // Always 200 for JSON-RPC
+        response.ContentType = "application/json";
+        await using var writer = new StreamWriter(response.OutputStream);
+        await writer.WriteAsync(JsonSerializer.Serialize(errorResponse));
+    }
+
+    private static async Task HandleInitializationRequest(HttpListenerResponse response, JsonRpcRequest jsonRpcRequest)
+    {
+        // We don't need to validate the client's initialization request for the test
+        // Just send back a valid server initialization response
+        var jsonRpcResponse = new JsonRpcResponse()
+        {
+            Id = jsonRpcRequest.Id,
+            Result = new
+            {
+                protocolVersion = "2024-11-05",
+                capabilities = new
+                {
+                    experimental = (object?)null,
+                    roots = (object?)null,
+                    sampling = (object?)null
+                },
+                serverInfo = new
+                {
+                    name = "ExampleServer",
+                    version = "1.0.0"
+                }
+            }
+        };
+
+        // Echo back to the HTTP response
+        response.StatusCode = 200;
+        response.ContentType = "application/json";
+
+        await using var writer = new StreamWriter(response.OutputStream);
+        await writer.WriteAsync(JsonSerializer.Serialize(jsonRpcResponse));
+    }
+
+    /// <summary>
+    /// Broadcast a message to all currently connected SSE clients.
+    /// </summary>
+    /// <param name="message">The raw string to send</param>
+    public async Task BroadcastMessageAsync(string message)
+    {
+        foreach (var client in _sseClients.ToArray()) // ToArray to avoid mutation issues
+        {
+            try
+            {
+                // SSE requires "event: <name>" + "data: <payload>" + blank line
+                await client.WriteLineAsync("event: message");
+                await client.WriteLineAsync($"data: {message}");
+                await client.WriteLineAsync();
+                await client.FlushAsync();
+            }
+            catch (IOException)
+            {
+                // Client may have disconnected. We let them get cleaned up on next iteration.
+            }
+            catch (ObjectDisposedException)
+            {
+                // Stream is disposed, ignore.
+            }
+        }
+    }
+
+    public async ValueTask DisposeAsync()
+    {
+        await _cts.CancelAsync();
+
+        if (_serverTask != null)
+        {
+            try
+            {
+                await Task.WhenAny(_serverTask, Task.Delay(2000));
+            }
+            catch (TaskCanceledException)
+            {
+                // ignore
+            }
+        }
+
+        _listener.Close();
+        _cts.Dispose();
+
+        _logger.LogInformation("Test SSE server stopped");
+    }
+
+    /// <summary>
+    /// Send a test notification to all connected SSE clients.
+    /// </summary>
+    /// <param name="content"></param>
+    /// <returns></returns>
+    public async Task SendTestNotificationAsync(string content)
+    {
+        var notification = new JsonRpcNotification
+        {
+            JsonRpc = "2.0",
+            Method = "test/notification",
+            Params = new { message = content }
+        };
+
+        var serialized = JsonSerializer.Serialize(notification);
+        await BroadcastMessageAsync(serialized);
+    }
+}

tests/mcpdotnet.Tests/mcpdotnet.Tests.csproj

@@ -32,6 +32,7 @@
   <ItemGroup>
     <ProjectReference Include="..\..\src\mcpdotnet\mcpdotnet.csproj" />
     <ProjectReference Include="..\mcpdotnet.TestServer\mcpdotnet.TestServer.csproj" />
+    <ProjectReference Include="..\mcpdotnet.TestSseServer\mcpdotnet.TestSseServer.csproj" />
   </ItemGroup>
 
   <ItemGroup>
@@ -41,6 +42,12 @@
     <Content Condition="$([MSBuild]::IsOSPlatform('Linux'))" Include="..\mcpdotnet.TestServer\bin\$(Configuration)\net8.0\TestServer.dll">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
+    <Content Condition="$([MSBuild]::IsOSPlatform('Windows'))" Include="..\mcpdotnet.TestSseServer\bin\$(Configuration)\net8.0\TestSseServer.exe">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+    <Content Condition="$([MSBuild]::IsOSPlatform('Linux'))" Include="..\mcpdotnet.TestSseServer\bin\$(Configuration)\net8.0\TestSseServer.dll">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
   </ItemGroup>
 
 </Project>