# Stdio and HTTP for MCP Servers

> Source: <https://www.dotnetperls.com/2026_7_27_stdio-http-mcp-servers>
> Published: 2026-07-27 07:00:00+00:00

I rewrote my **MCP server** to use **Stdio** input and output instead of HTTP. An MCP server that uses Stdio still receives and returns JSON-formatted messages, but no HTTP connection is made. Instead, a client (like `llama-cpp`

) uses a sub-process to interact with the MCP server.

In this sense, a Stdio MCP server is not a real "server" but is just a regular **console program**. In any case, I used the Rust crate `RMcp`

, which allowed me to replace 300 lines of code with about 60 lines of code.

With `RMcp`

, it is possible to generate most of the necessary code with just Rust **derive** attributes.

In `llama-cpp`

, Stdio MCP server support was added just **a couple days ago**. To add an Stdio MCP server, use the `mcp-servers-json`

or `mcp-servers-config`

arguments to `llama-server`

, and specify a JSON object that defines `mcpServers`

. This is the mcp.json file format. The MCP server tools will appear in the **built-in tools** in `llama-cpp`

's web UI.