Move the SseResponseStreamTransport out of sample

Directory.Packages.props

@@ -13,7 +13,7 @@
     <PackageVersion Include="Microsoft.Extensions.AI.Abstractions" Version="$(MicrosoftExtensionsAIVersion)" />
     <PackageVersion Include="Microsoft.Extensions.Hosting.Abstractions" Version="$(MicrosoftExtensionsVersion)" />
     <PackageVersion Include="Microsoft.Extensions.Logging.Abstractions" Version="$(MicrosoftExtensionsVersion)" />
-    <PackageVersion Include="System.Net.ServerSentEvents" Version="$(SystemVersion)" />
+    <PackageVersion Include="System.Net.ServerSentEvents" Version="$(System10Version)" />
     <PackageVersion Include="System.Text.Json" Version="$(SystemVersion)" />
     <PackageVersion Include="System.Threading.Channels" Version="$(SystemVersion)" />
 

samples/AspNetCoreSseServer/AspNetCoreSseServer.csproj

@@ -10,8 +10,4 @@
     <ProjectReference Include="..\..\src\ModelContextProtocol\ModelContextProtocol.csproj" />
   </ItemGroup>
 
-  <ItemGroup>
-    <PackageReference Include="System.Net.ServerSentEvents" VersionOverride="10.0.0-preview.1.25080.5" />
-  </ItemGroup>
-
 </Project>

samples/AspNetCoreSseServer/McpEndpointRouteBuilderExtensions.cs

@@ -2,6 +2,7 @@
 using ModelContextProtocol.Server;
 using ModelContextProtocol.Utils.Json;
 using Microsoft.Extensions.Options;
+using ModelContextProtocol.Protocol.Transport;
 
 namespace AspNetCoreSseServer;
 
@@ -10,15 +11,15 @@ public static class McpEndpointRouteBuilderExtensions
     public static IEndpointConventionBuilder MapMcpSse(this IEndpointRouteBuilder endpoints)
     {
         IMcpServer? server = null;
-        SseServerStreamTransport? transport = null;
+        SseResponseStreamTransport? transport = null;
         var loggerFactory = endpoints.ServiceProvider.GetRequiredService<ILoggerFactory>();
         var mcpServerOptions = endpoints.ServiceProvider.GetRequiredService<IOptions<McpServerOptions>>();
 
         var routeGroup = endpoints.MapGroup("");
 
         routeGroup.MapGet("/sse", async (HttpResponse response, CancellationToken requestAborted) =>
         {
-            await using var localTransport = transport = new SseServerStreamTransport(response.Body);
+            await using var localTransport = transport = new SseResponseStreamTransport(response.Body);
             await using var localServer = server = McpServerFactory.Create(transport, mcpServerOptions.Value, loggerFactory, endpoints.ServiceProvider);
 
             await localServer.StartAsync(requestAborted);
@@ -37,7 +38,7 @@ public static IEndpointConventionBuilder MapMcpSse(this IEndpointRouteBuilder en
             }
         });
 
-        routeGroup.MapPost("/message", async (HttpContext context) =>
+        routeGroup.MapPost("/message", async context =>
         {
             if (transport is null)
             {

src/ModelContextProtocol/Protocol/Transport/HttpListenerSseServerTransport.cs

@@ -1,4 +1,5 @@
-using System.Text.Json;
+using System.Net;
+using System.Text.Json;
 using Microsoft.Extensions.Logging;
 using ModelContextProtocol.Protocol.Messages;
 using ModelContextProtocol.Utils.Json;
@@ -9,7 +10,7 @@
 namespace ModelContextProtocol.Protocol.Transport;
 
 /// <summary>
-/// Implements the MCP transport protocol over standard input/output streams.
+/// Implements the MCP transport protocol using <see cref="HttpListener"/>.
 /// </summary>
 public sealed class HttpListenerSseServerTransport : TransportBase, IServerTransport
 {

samples/AspNetCoreSseServer/SseServerStreamTransport.cs → src/ModelContextProtocol/Protocol/Transport/SseResponseStreamTransport.cs

@@ -3,21 +3,31 @@
 using System.Text.Json;
 using System.Threading.Channels;
 using ModelContextProtocol.Protocol.Messages;
-using ModelContextProtocol.Protocol.Transport;
 using ModelContextProtocol.Utils.Json;
 
-namespace AspNetCoreSseServer;
+namespace ModelContextProtocol.Protocol.Transport;
 
-public class SseServerStreamTransport(Stream sseResponseStream) : ITransport
+/// <summary>
+/// Implements the MCP SSE server transport protocol using the SSE response <see cref="Stream"/>.
+/// </summary>
+/// <param name="sseResponseStream">The stream to write the SSE response body to.</param>
+public sealed class SseResponseStreamTransport(Stream sseResponseStream) : ITransport
 {
     private readonly Channel<IJsonRpcMessage> _incomingChannel = CreateSingleItemChannel<IJsonRpcMessage>();
     private readonly Channel<SseItem<IJsonRpcMessage?>> _outgoingSseChannel = CreateSingleItemChannel<SseItem<IJsonRpcMessage?>>();
 
     private Task? _sseWriteTask;
     private Utf8JsonWriter? _jsonWriter;
 
+    /// <inherityydoc/>
     public bool IsConnected => _sseWriteTask?.IsCompleted == false;
 
+    /// <summary>
+    /// Starts the transport and writes the JSON-RPC messages sent via <see cref="SendMessageAsync(IJsonRpcMessage, CancellationToken)"/>
+    /// to the SSE response stream until cancelled or disposed.
+    /// </summary>
+    /// <param name="cancellationToken">A token to cancel writing to the SSE response stream.</param>
+    /// <returns>A task representing the send loop that writes JSON-RPC messages to the SSE response stream.</returns>
     public Task RunAsync(CancellationToken cancellationToken)
     {
         void WriteJsonRpcMessageToBuffer(SseItem<IJsonRpcMessage?> item, IBufferWriter<byte> writer)
@@ -28,7 +38,7 @@ void WriteJsonRpcMessageToBuffer(SseItem<IJsonRpcMessage?> item, IBufferWriter<b
                 return;
             }
 
-            JsonSerializer.Serialize(GetUtf8JsonWriter(writer), item.Data, McpJsonUtilities.DefaultOptions);
+            JsonSerializer.Serialize(GetUtf8JsonWriter(writer), item.Data, McpJsonUtilities.DefaultOptions.GetTypeInfo<IJsonRpcMessage?>());
         }
 
         // The very first SSE event isn't really an IJsonRpcMessage, but there's no API to write a single item of a different type,
@@ -39,23 +49,40 @@ void WriteJsonRpcMessageToBuffer(SseItem<IJsonRpcMessage?> item, IBufferWriter<b
         return _sseWriteTask = SseFormatter.WriteAsync(sseItems, sseResponseStream, WriteJsonRpcMessageToBuffer, cancellationToken);
     }
 
+    /// <inheritdoc/>
     public ChannelReader<IJsonRpcMessage> MessageReader => _incomingChannel.Reader;
 
+    /// <inheritdoc/>
     public ValueTask DisposeAsync()
     {
         _incomingChannel.Writer.TryComplete();
         _outgoingSseChannel.Writer.TryComplete();
         return new ValueTask(_sseWriteTask ?? Task.CompletedTask);
     }
 
-    public Task SendMessageAsync(IJsonRpcMessage message, CancellationToken cancellationToken = default) =>
-        _outgoingSseChannel.Writer.WriteAsync(new SseItem<IJsonRpcMessage?>(message), cancellationToken).AsTask();
+    /// <inheritdoc/>
+    public Task SendMessageAsync(IJsonRpcMessage message, CancellationToken cancellationToken = default)
+    {
+        if (_sseWriteTask is null)
+        {
+            throw new InvalidOperationException($"Transport is not connected. Make sure to call {nameof(RunAsync)} first.");
+        }
+
+        return _outgoingSseChannel.Writer.WriteAsync(new SseItem<IJsonRpcMessage?>(message), cancellationToken).AsTask();
+    }
 
+    /// <summary>
+    /// Handles incoming JSON-RPC messages received on the /message endpoint.
+    /// </summary>
+    /// <param name="message">The JSON-RPC message received.</param>
+    /// <param name="cancellationToken">A token to cancel the operation.</param>
+    /// <returns>A task representing the potentially asynchronous operation to buffer or process the JSON-RPC message.</returns>
+    /// <exception cref="InvalidOperationException">Thrown when there is an attempt to process a message before calling <see cref="RunAsync(CancellationToken)"/>.</exception>
     public Task OnMessageReceivedAsync(IJsonRpcMessage message, CancellationToken cancellationToken)
     {
-        if (!IsConnected)
+        if (_sseWriteTask is null)
         {
-            throw new McpTransportException("Transport is not connected");
+            throw new InvalidOperationException($"Transport is not connected. Make sure to call {nameof(RunAsync)} first.");
         }
 
         return _incomingChannel.Writer.WriteAsync(message, cancellationToken).AsTask();