Function handleJsonRpc

docker/mcp-stdio-proxy/server.mjs:69–151

* Handle a JSON-RPC request by forwarding to the stdio MCP client. * * This bypasses the MCP SDK's Server class which only accepts one `initialize` * per lifetime. By handling JSON-RPC directly, we support unlimited HTTP clients * (e.g. worker for discovery, then gateway for tool calls) sharing

(req, res, stdioClient, name)

 * (e.g. worker for discovery, then gateway for tool calls) sharing one stdio server.
 */
async function handleJsonRpc(req, res, stdioClient, name) {
  const body = req.body;

  // Notifications have no `id` — return 202 Accepted (expected by MCP SDK client)
  if (body && body.method && body.id === undefined) {
    return res.status(202).end();
  }

  if (!body || !body.method) {
    return res.status(400).json({
      jsonrpc: '2.0',
      id: body?.id ?? null,
      error: { code: -32600, message: 'Invalid request: missing method' },
    });
  }

  try {
    switch (body.method) {
      case 'initialize': {
        const result = {
          protocolVersion: LATEST_PROTOCOL_VERSION,
          capabilities: stdioClient.getServerCapabilities() ?? { tools: { listChanged: false } },
          serverInfo: stdioClient.getServerVersion() ?? {
            name: `mcp-proxy-${name}`,
            version: '1.0.0',
          },
          instructions: stdioClient.getInstructions?.(),
        };
        return res.json({ jsonrpc: '2.0', id: body.id, result });
      }

      case 'tools/list': {
        const result = await stdioClient.listTools();
        return res.json({ jsonrpc: '2.0', id: body.id, result });
      }

      case 'tools/call': {
        const result = await stdioClient.callTool({
          name: body.params.name,
          arguments: body.params.arguments ?? {},
        });
        return res.json({ jsonrpc: '2.0', id: body.id, result });
      }

      case 'resources/list': {
        const result = await stdioClient.listResources();
        return res.json({ jsonrpc: '2.0', id: body.id, result });
      }

      case 'resources/read': {
        const result = await stdioClient.readResource({ uri: body.params.uri });
        return res.json({ jsonrpc: '2.0', id: body.id, result });
      }

      case 'prompts/list': {
        const result = await stdioClient.listPrompts();
        return res.json({ jsonrpc: '2.0', id: body.id, result });
      }