stdioTransport.ts•3.38 kB
/**
* @fileoverview Handles the setup and connection for the Stdio MCP transport.
* Implements the MCP Specification 2025-03-26 for stdio transport.
* This transport communicates directly over standard input (stdin) and
* standard output (stdout), typically used when the MCP server is launched
* as a child process by a host application.
*
* Specification Reference:
* https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/docs/specification/2025-03-26/basic/transports.mdx#stdio
*
* --- Authentication Note ---
* As per the MCP Authorization Specification (2025-03-26, Section 1.2),
* STDIO transports SHOULD NOT implement HTTP-based authentication flows.
* Authorization is typically handled implicitly by the host application
* controlling the server process. This implementation follows that guideline.
*
* @see {@link https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/docs/specification/2025-03-26/basic/authorization.mdx | MCP Authorization Specification}
* @module src/mcp-server/transports/stdioTransport
*/
import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { ErrorHandler, logger, RequestContext } from "../../utils/index.js";
/**
* Connects a given `McpServer` instance to the Stdio transport.
* This function initializes the SDK's `StdioServerTransport`, which manages
* communication over `process.stdin` and `process.stdout` according to the
* MCP stdio transport specification.
*
* MCP Spec Points Covered by SDK's `StdioServerTransport`:
* - Reads JSON-RPC messages (requests, notifications, responses, batches) from stdin.
* - Writes JSON-RPC messages to stdout.
* - Handles newline delimiters and ensures no embedded newlines in output messages.
* - Ensures only valid MCP messages are written to stdout.
*
* Logging via the `logger` utility MAY result in output to stderr, which is
* permitted by the spec for logging purposes.
*
* @param server - The `McpServer` instance.
* @param parentContext - The logging and tracing context from the calling function.
* @returns A promise that resolves when the Stdio transport is successfully connected.
* @throws {Error} If the connection fails during setup.
*/
export async function connectStdioTransport(
server: McpServer,
parentContext: RequestContext,
): Promise<void> {
const operationContext = {
...parentContext,
operation: "connectStdioTransport",
transportType: "Stdio",
};
logger.debug("Attempting to connect stdio transport...", operationContext);
try {
logger.debug("Creating StdioServerTransport instance...", operationContext);
const transport = new StdioServerTransport();
logger.debug(
"Connecting McpServer instance to StdioServerTransport...",
operationContext,
);
await server.connect(transport);
logger.info(
"MCP Server connected and listening via stdio transport.",
operationContext,
);
if (process.stdout.isTTY) {
console.log(
`\n🚀 MCP Server running in STDIO mode.\n (MCP Spec: 2025-03-26 Stdio Transport)\n`,
);
}
} catch (err) {
ErrorHandler.handleError(err, { ...operationContext, critical: true });
throw err; // Re-throw after handling to allow caller to react if necessary
}
}