Echo MCP Server

Okay, here's a basic outline and code example for a Model Context Protocol (MCP) server implementing an echo service using .NET Core. Since MCP isn't a widely standardized protocol, I'll make some assumptions about its structure. I'll assume it's a text-based protocol where messages are delimited by a newline character (`\n`). You'll likely need to adapt this to your specific MCP definition. **Conceptual Overview** 1. **Server Setup:** Create a TCP listener to accept incoming connections. 2. **Connection Handling:** For each connection, create a new thread or task to handle it concurrently. 3. **Receive Data:** Read data from the client socket. 4. **Parse MCP Message:** Parse the received data according to your MCP specification. In this simple echo example, we'll just treat the entire line as the message. 5. **Echo Response:** Send the received message back to the client. 6. **Close Connection:** Close the socket when the client disconnects or an error occurs. **Code Example (.NET Core)** ```csharp using System; using System.Net; using System.Net.Sockets; using System.Text; using System.Threading.Tasks; namespace McpEchoServer { class Program { private static int _port = 12345; // Change this to your desired port private static IPAddress _ipAddress = IPAddress.Any; // Listen on all interfaces static async Task Main(string[] args) { TcpListener listener = null; try { listener = new TcpListener(_ipAddress, _port); listener.Start(); Console.WriteLine($"MCP Echo Server started on {_ipAddress}:{_port}"); while (true) { TcpClient client = await listener.AcceptTcpClientAsync(); Console.WriteLine($"Accepted new client: {client.Client.RemoteEndPoint}"); _ = HandleClientAsync(client); // Fire and forget - handle client in a separate task } } catch (Exception e) { Console.WriteLine($"An error occurred: {e}"); } finally { listener?.Stop(); } Console.WriteLine("Server stopped."); } static async Task HandleClientAsync(TcpClient client) { try { using (NetworkStream stream = client.GetStream()) using (var reader = new System.IO.StreamReader(stream, Encoding.UTF8)) using (var writer = new System.IO.StreamWriter(stream, Encoding.UTF8) { AutoFlush = true }) // AutoFlush ensures data is sent immediately { string message; while ((message = await reader.ReadLineAsync()) != null) { Console.WriteLine($"Received: {message} from {client.Client.RemoteEndPoint}"); // Echo the message back await writer.WriteLineAsync(message); Console.WriteLine($"Sent: {message} to {client.Client.RemoteEndPoint}"); } Console.WriteLine($"Client disconnected: {client.Client.RemoteEndPoint}"); } } catch (Exception e) { Console.WriteLine($"Error handling client {client.Client.RemoteEndPoint}: {e}"); } finally { client.Close(); } } } } ``` **How to Use:** 1. **Create a new .NET Core Console Application:** In Visual Studio or using the .NET CLI (`dotnet new console`). 2. **Replace the `Program.cs` content:** Paste the code above into your `Program.cs` file. 3. **Adjust the Port:** Change the `_port` variable to the port you want the server to listen on. 4. **Run the Server:** Build and run the application. You should see the "MCP Echo Server started" message. **Client Example (Simple Telnet or Netcat)** You can test this server using a simple Telnet client or Netcat. * **Telnet:** Open a command prompt or terminal and type: `telnet localhost 12345` (replace `12345` with your port). Then type some text and press Enter. You should see the same text echoed back. * **Netcat (nc):** `nc localhost 12345`. Type some text and press Enter. **Explanation:** * **`TcpListener`:** Listens for incoming TCP connections on the specified IP address and port. * **`AcceptTcpClientAsync()`:** Asynchronously accepts a pending connection request. This returns a `TcpClient` object representing the connected client. * **`HandleClientAsync()`:** This `async` method handles the communication with a single client. It's launched as a separate task using `_ = HandleClientAsync(client);` so that the server can handle multiple clients concurrently. * **`NetworkStream`:** Provides access to the underlying network stream of the `TcpClient`. * **`StreamReader` and `StreamWriter`:** Used for reading and writing text data to the stream. `StreamReader.ReadLineAsync()` reads a line of text from the stream asynchronously. `StreamWriter.WriteLineAsync()` writes a line of text to the stream asynchronously. `AutoFlush = true` ensures that data is sent immediately. * **`Encoding.UTF8`:** Specifies the character encoding to use for reading and writing text. * **`client.Close()`:** Closes the connection to the client. * **Error Handling:** The `try...catch...finally` blocks provide basic error handling. **Important Considerations and Improvements:** * **MCP Specification:** This example assumes a very simple MCP protocol. You'll need to adapt the parsing and message handling logic to match your actual MCP specification. This might involve parsing headers, message types, data lengths, etc. * **Error Handling:** The error handling is basic. You should add more robust error handling to catch exceptions and handle them gracefully. Consider logging errors. * **Threading/Task Management:** The `_ = HandleClientAsync(client);` approach is a simple way to launch a task, but for a production server, you might want to use a more sophisticated task management strategy (e.g., using a `TaskScheduler` or a thread pool) to control the number of concurrent tasks. * **Security:** This example is not secure. If you're transmitting sensitive data, you should use TLS/SSL to encrypt the connection. * **Message Framing:** If your MCP protocol doesn't use newline characters as delimiters, you'll need to implement a different message framing mechanism (e.g., using a fixed-length header that specifies the message length). * **Asynchronous Operations:** The use of `async` and `await` makes the server more scalable by allowing it to handle multiple clients concurrently without blocking threads. * **Logging:** Implement a logging mechanism to record server events, errors, and client interactions. This is crucial for debugging and monitoring. * **Configuration:** Externalize configuration settings (e.g., port number, IP address) into a configuration file. **Chinese Translation of Key Concepts:** * **Model Context Protocol (MCP):** 模型上下文协议 (Móxíng shàngxiàwén xiéyì) * **Echo Service:** 回显服务 (Huíxiǎn fúwù) * **.NET Core:** .NET Core * **TCP Listener:** TCP 监听器 (TCP jiāntīng qì) * **Socket:** 套接字 (Tàojiēzì) * **Network Stream:** 网络流 (Wǎngluò liú) * **Asynchronous:** 异步 (Yìbù) * **Thread:** 线程 (Xiànchéng) * **Task:** 任务 (Rènwù) * **Client:** 客户端 (Kèhùduān) * **Server:** 服务器 (Fúwùqì) * **Port:** 端口 (Duānkǒu) * **IP Address:** IP 地址 (IP dìzhǐ) * **Encoding:** 编码 (Biānmǎ) * **Message:** 消息 (Xiāoxī) * **Delimiter:** 分隔符 (Fēngéfú) This comprehensive example should give you a good starting point for building your MCP echo server in .NET Core. Remember to adapt the code to your specific MCP protocol requirements. Good luck!