Server support (stdio) (#19)

* Server support (stdio)
* TestServer project
* Refactored McpClient class to extract shared endpoint logic (with McpServer) to a base class, McpJsonRpcEndpoint.
* Improved xmldoc comments for protocol types, mirroring specification schema comments.
* Update README.MD

src/mcpdotnet/Protocol/Transport/StdioServerTransport.cs

@@ -0,0 +1,195 @@
+using System.Text.Json;
+using Microsoft.Extensions.Logging;
+using McpDotNet.Protocol.Messages;
+using McpDotNet.Utils.Json;
+using McpDotNet.Logging;
+
+namespace McpDotNet.Protocol.Transport;
+
+/// <summary>
+/// Implements the MCP transport protocol over standard input/output streams.
+/// </summary>
+public sealed class StdioServerTransport : TransportBase, IServerTransport
+{
+    private readonly string _serverName;
+    private readonly ILogger<StdioClientTransport> _logger;
+    private readonly JsonSerializerOptions _jsonOptions;
+    private Task? _readTask;
+    private CancellationTokenSource? _shutdownCts;
+
+    private string EndpointName => $"Server (stdio) ({_serverName})";
+
+    /// <summary>
+    /// Initializes a new instance of the StdioServerTransport class.
+    /// </summary>
+    /// <param name="serverName">The name of the server.</param>
+    /// <param name="loggerFactory">A logger factory for creating loggers.</param>
+    public StdioServerTransport(string serverName, ILoggerFactory loggerFactory)
+        : base(loggerFactory)
+    {
+        _serverName = serverName;
+        _logger = loggerFactory.CreateLogger<StdioClientTransport>();
+        _jsonOptions = new JsonSerializerOptions().ConfigureForMcp(loggerFactory);
+    }
+
+    /// <inheritdoc/>
+    public Task StartListeningAsync(CancellationToken cancellationToken = default)
+    {
+        _shutdownCts = new CancellationTokenSource();
+
+        _readTask = Task.Run(async () => await ReadMessagesAsync(_shutdownCts.Token));
+
+        SetConnected(true);
+
+        return Task.CompletedTask;
+    }
+
+
+    /// <inheritdoc/>
+    public override async Task SendMessageAsync(IJsonRpcMessage message, CancellationToken cancellationToken = default)
+    {
+        if (!IsConnected)
+        {
+            _logger.TransportNotConnected(EndpointName);
+            throw new McpTransportException("Transport is not connected");
+        }
+
+        string id = "(no id)";
+        if (message is IJsonRpcMessageWithId messageWithId)
+        {
+            id = messageWithId.Id.ToString();
+        }
+
+        try
+        {
+            var json = JsonSerializer.Serialize(message, _jsonOptions);
+            _logger.TransportSendingMessage(EndpointName, id, json);
+            
+            using (Console.OpenStandardOutput())
+            {
+                await Console.Out.WriteLineAsync(json.AsMemory(), cancellationToken);
+                await Console.Out.FlushAsync();
+            }
+
+            _logger.TransportSentMessage(EndpointName, id);
+        }
+        catch (Exception ex)
+        {
+            _logger.TransportSendFailed(EndpointName, id, ex);
+            throw new McpTransportException("Failed to send message", ex);
+        }
+    }
+
+    /// <inheritdoc/>
+    public override async ValueTask DisposeAsync()
+    {
+        await CleanupAsync(CancellationToken.None);
+        GC.SuppressFinalize(this);
+    }
+
+    private async Task ReadMessagesAsync(CancellationToken cancellationToken)
+    {
+        try
+        {
+            _logger.TransportEnteringReadMessagesLoop(EndpointName);
+
+            while (!cancellationToken.IsCancellationRequested)
+            {
+                _logger.TransportWaitingForMessage(EndpointName);
+                using (Console.OpenStandardInput())
+                {
+                    var reader = Console.In;
+                    var line = await reader.ReadLineAsync(cancellationToken);
+                    if (line == null)
+                    {
+                        _logger.TransportEndOfStream(EndpointName);
+                        break;
+                    }
+
+                    if (string.IsNullOrWhiteSpace(line))
+                    {
+                        continue;
+                    }
+
+                    _logger.TransportReceivedMessage(EndpointName, line);
+
+                    try
+                    {
+                        var message = JsonSerializer.Deserialize<IJsonRpcMessage>(line, _jsonOptions);
+                        if (message != null)
+                        {
+                            string messageId = "(no id)";
+                            if (message is IJsonRpcMessageWithId messageWithId)
+                            {
+                                messageId = messageWithId.Id.ToString();
+                            }
+                            _logger.TransportReceivedMessageParsed(EndpointName, messageId);
+                            await WriteMessageAsync(message, cancellationToken);
+                            _logger.TransportMessageWritten(EndpointName, messageId);
+                        }
+                        else
+                        {
+                            _logger.TransportMessageParseUnexpectedType(EndpointName, line);
+                        }
+                    }
+                    catch (JsonException ex)
+                    {
+                        _logger.TransportMessageParseFailed(EndpointName, line, ex);
+                        // Continue reading even if we fail to parse a message
+                    }
+                }
+            }
+            _logger.TransportExitingReadMessagesLoop(EndpointName);
+        }
+        catch (OperationCanceledException)
+        {
+            _logger.TransportReadMessagesCancelled(EndpointName);
+            // Normal shutdown
+        }
+        catch (Exception ex)
+        {
+            _logger.TransportReadMessagesFailed(EndpointName, ex);
+        }
+        finally
+        {
+            await CleanupAsync(cancellationToken);
+        }
+    }
+
+    private async Task CleanupAsync(CancellationToken cancellationToken)
+    {
+        _logger.TransportCleaningUp(EndpointName);
+        
+        _shutdownCts?.Cancel();
+        _shutdownCts?.Dispose();
+        _shutdownCts = null;
+
+        if (_readTask != null)
+        {
+            try
+            {
+                _logger.TransportWaitingForReadTask(EndpointName);
+                await _readTask.WaitAsync(TimeSpan.FromSeconds(5), cancellationToken);
+            }
+            catch (TimeoutException)
+            {
+                _logger.TransportCleanupReadTaskTimeout(EndpointName);
+                // Continue with cleanup
+            }
+            catch (OperationCanceledException)
+            {
+                _logger.TransportCleanupReadTaskCancelled(EndpointName);
+                // Ignore cancellation
+            }
+            catch (Exception ex)
+            {
+                _logger.TransportCleanupReadTaskFailed(EndpointName, ex);
+            }
+            _readTask = null;
+            _logger.TransportReadTaskCleanedUp(EndpointName);
+        }
+
+        SetConnected(false);
+        _logger.TransportCleanedUp(EndpointName);
+    }
+}