C SDK with Paho MQTT

This guide demonstrates how to use the MCP over MQTT C SDK with Paho MQTT to create a simple MCP over MQTT server. Currently, only the MCP server is supported. You can use the Python SDK to create an MCP client for interaction.

Create an MCP Server

Following the instructions in the C SDK with Paho MQTT README, after installing the dependencies and SDK, create a file named demo_mcp_server.c and add the following code:

#include "mcp_server.h"

// Callback function to get temperature
const char* get_temperature_callback(int n_args, property_t *args) {
    // Read sensor data
    float temp = read_temperature_sensor();

    // Return JSON formatted result
    static char result[64];
    snprintf(result, sizeof(result), "{\"temperature\": %.2f}", temp);
    return result;
}

// Define MCP tools
mcp_tool_t my_tools[] = {
    {
        .name = "get_temperature",
        .description = "Get device temperature",
        .property_count = 0,
        .properties = NULL,
        .call = get_temperature_callback
    }
};

// Initialize MCP server
mcp_server_t *server = mcp_server_init(
    "sensor",                // Server name
    "Sensor MCP Server",     // Description
    "mqtt://broker.example.com", // MQTT Broker URI
    "client_001",            // Client ID
    "username",              // Username
    "password",              // Password
    NULL                     // Certificate (optional)
);

// Register tools
mcp_server_register_tool(server, 1, my_tools);

// Start server
mcp_server_run(server);

Create and Run an MCP Client with Python SDK

Refer to the Python SDK documentation to create an MCP client that connects to the MCP server created above and invokes the get_temperature tool.

Build and Compile the MCP Server with CMake

You can follow the CMake examples provided in the paho-mcp-over-mqtt repository.

After building, run the generated executable to start the MCP server:

./demo_mcp_server