Am i doing anything wrong with this MCP client server combo?

[ZedDevStuff]

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• I have checked that this question would not be more appropriate as an issue in a specific repository
• I have searched existing discussions and documentation for answers

Question Category

• Protocol Specification
• SDK Usage
• Server Implementation
• General Implementation
• Documentation
• Other

Your Question

I've been trying to embed an MCP server in an android app but came across a few problems, so i decided to experiment on a console app first. The following code doesn't seem to work at all. CreateClient never completes. Am i misunderstanding something?

internal class Program
{
    public static Stream InputStream;
    public static Stream OutputStream;
    static async Task Main(string[] args)
    {
        InputStream = new MemoryStream();
        OutputStream = new MemoryStream();
        await StartServer();
        await StartClient();
    }

    public static async Task StartServer()
    {
        var builder = Host.CreateApplicationBuilder();
        builder.Logging.AddConsole(opt =>
        {
            opt.LogToStandardErrorThreshold = LogLevel.Trace;
        });
        builder.Services.AddMcpServer()
            .WithToolsFromAssembly()
            .WithStreamServerTransport(InputStream, OutputStream);
        await builder.Build().StartAsync();
    }
    public static async Task StartClient()
    {
        McpClient client = await McpClient.CreateAsync(new StreamClientTransport(InputStream, OutputStream));
        var tools = await client.ListToolsAsync();
        foreach (var tool in tools)
            Console.WriteLine(tool);
        Console.ReadLine();
        await client.DisposeAsync();
    }
}
[McpServerToolType]
public class Tools
{
    [McpServerTool]
    public int RandomNumber()
    {
        return new Random().Next();
    }
}

[PederHP]

Yes, you are not supposed to have your server and client in the same process. There are ways to make that work, but it's usually not what you want, as you'll need an InMemoryTransport for it, and you might as well just use AITool instead.

Take a look at the examples over at Microsoft.Extensions.AI - if it's all in a single application you don't need MCP at all, you can create AITool objects directly from methods via AIFunctionFactory.

See: https://learn.microsoft.com/en-us/dotnet/ai/microsoft-extensions-ai

[ZedDevStuff]

That's what i was doing before but i got interested in MCPs since on desktop it would allow me to use them in multiple apps without copying the code. I could technically run the MCP in an Android Service too