chore: extract pure mcp server helpers (#751)

src/browserServerBackend.ts

@@ -0,0 +1,66 @@
+/**
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { FullConfig } from './config.js';
+import { Context } from './context.js';
+import { logUnhandledError } from './log.js';
+import { Response } from './response.js';
+import { SessionLog } from './sessionLog.js';
+import { filteredTools } from './tools.js';
+import { packageJSON } from './package.js';
+
+import type { BrowserContextFactory } from './browserContextFactory.js';
+import type * as mcpServer from './mcp/server.js';
+import type { ServerBackend } from './mcp/server.js';
+import type { Tool } from './tools/tool.js';
+
+export class BrowserServerBackend implements ServerBackend {
+  name = 'Playwright';
+  version = packageJSON.version;
+  private _tools: Tool[];
+  private _context: Context;
+  private _sessionLog: SessionLog | undefined;
+
+  constructor(config: FullConfig, browserContextFactory: BrowserContextFactory) {
+    this._tools = filteredTools(config);
+    this._context = new Context(this._tools, config, browserContextFactory);
+  }
+
+  async initialize() {
+    this._sessionLog = this._context.config.saveSession ? await SessionLog.create(this._context.config) : undefined;
+  }
+
+  tools(): mcpServer.ToolSchema<any>[] {
+    return this._tools.map(tool => tool.schema);
+  }
+
+  async callTool(schema: mcpServer.ToolSchema<any>, parsedArguments: any) {
+    const response = new Response(this._context, schema.name, parsedArguments);
+    const tool = this._tools.find(tool => tool.schema.name === schema.name)!;
+    await tool.handle(this._context, parsedArguments, response);
+    if (this._sessionLog)
+      await this._sessionLog.log(response);
+    return await response.serialize();
+  }
+
+  serverInitialized(version: mcpServer.ClientVersion | undefined) {
+    this._context.clientVersion = version;
+  }
+
+  serverClosed() {
+    void this._context.dispose().catch(logUnhandledError);
+  }
+}

src/connection.ts

@@ -1,84 +0,0 @@
-/**
- * Copyright (c) Microsoft Corporation.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-import { Server } from '@modelcontextprotocol/sdk/server/index.js';
-import { CallToolRequestSchema, ListToolsRequestSchema, Tool as McpTool } from '@modelcontextprotocol/sdk/types.js';
-import { zodToJsonSchema } from 'zod-to-json-schema';
-import { Context } from './context.js';
-import { Response } from './response.js';
-import { packageJSON } from './package.js';
-import { FullConfig } from './config.js';
-import { SessionLog } from './sessionLog.js';
-import { logUnhandledError } from './log.js';
-import type { BrowserContextFactory } from './browserContextFactory.js';
-import type { Tool } from './tools/tool.js';
-
-export async function createMCPServer(config: FullConfig, tools: Tool<any>[], browserContextFactory: BrowserContextFactory): Promise<Server> {
-  const context = new Context(tools, config, browserContextFactory);
-  const server = new Server({ name: 'Playwright', version: packageJSON.version }, {
-    capabilities: {
-      tools: {},
-    }
-  });
-
-  const sessionLog = config.saveSession ? await SessionLog.create(config) : undefined;
-
-  server.setRequestHandler(ListToolsRequestSchema, async () => {
-    return {
-      tools: tools.map(tool => ({
-        name: tool.schema.name,
-        description: tool.schema.description,
-        inputSchema: zodToJsonSchema(tool.schema.inputSchema),
-        annotations: {
-          title: tool.schema.title,
-          readOnlyHint: tool.schema.type === 'readOnly',
-          destructiveHint: tool.schema.type === 'destructive',
-          openWorldHint: true,
-        },
-      })) as McpTool[],
-    };
-  });
-
-  server.setRequestHandler(CallToolRequestSchema, async request => {
-    const errorResult = (...messages: string[]) => ({
-      content: [{ type: 'text', text: messages.join('\n') }],
-      isError: true,
-    });
-    const tool = tools.find(tool => tool.schema.name === request.params.name);
-    if (!tool)
-      return errorResult(`Tool "${request.params.name}" not found`);
-
-    try {
-      const response = new Response(context, request.params.name, request.params.arguments || {});
-      await tool.handle(context, tool.schema.inputSchema.parse(request.params.arguments || {}), response);
-      if (sessionLog)
-        await sessionLog.log(response);
-      return await response.serialize();
-    } catch (error) {
-      return errorResult(String(error));
-    }
-  });
-
-  server.oninitialized = () => {
-    context.clientVersion = server.getClientVersion();
-  };
-
-  server.onclose = () => {
-    void context.dispose().catch(logUnhandledError);
-  };
-
-  return server;
-}

src/extension/cdpRelay.ts

@@ -27,10 +27,9 @@ import { spawn } from 'child_process';
 import { WebSocket, WebSocketServer } from 'ws';
 import debug from 'debug';
 import * as playwright from 'playwright';
-import { httpAddressToString, startHttpServer } from '../transport.js';
 // @ts-ignore
 const { registry } = await import('playwright-core/lib/server/registry/index');
-
+import { httpAddressToString, startHttpServer } from '../httpServer.js';
 import type { BrowserContextFactory } from '../browserContextFactory.js';
 import type websocket from 'ws';
 

src/extension/main.ts

@@ -14,22 +14,14 @@
  * limitations under the License.
  */
 
-import { startHttpServer, startHttpTransport, startStdioTransport } from '../transport.js';
-import { Server } from '../server.js';
 import { startCDPRelayServer } from './cdpRelay.js';
-import { filteredTools } from '../tools.js';
+import { BrowserServerBackend } from '../browserServerBackend.js';
+import * as mcpTransport from '../mcp/transport.js';
 
 import type { FullConfig } from '../config.js';
 
 export async function runWithExtension(config: FullConfig) {
   const contextFactory = await startCDPRelayServer(config.browser.launchOptions.channel || 'chrome');
-  const server = new Server(config, filteredTools(config), contextFactory);
-  server.setupExitWatchdog();
-
-  if (config.server.port !== undefined) {
-    const httpServer = await startHttpServer(config.server);
-    startHttpTransport(httpServer, server);
-  } else {
-    await startStdioTransport(server);
-  }
+  const serverBackendFactory = () => new BrowserServerBackend(config, contextFactory);
+  await mcpTransport.start(serverBackendFactory, config.server);
 }

src/httpServer.ts

@@ -14,219 +14,31 @@
  * limitations under the License.
  */
 
-import fs from 'fs';
-import path from 'path';
+import assert from 'assert';
 import http from 'http';
-import net from 'net';
 
-import mime from 'mime';
+import type * as net from 'net';
 
-import { ManualPromise } from './manualPromise.js';
-
-
-export type ServerRouteHandler = (request: http.IncomingMessage, response: http.ServerResponse) => void;
-
-export type Transport = {
-  sendEvent?: (method: string, params: any) => void;
-  close?: () => void;
-  onconnect: () => void;
-  dispatch: (method: string, params: any) => Promise<any>;
-  onclose: () => void;
-};
-
-export class HttpServer {
-  private _server: http.Server;
-  private _urlPrefixPrecise: string = '';
-  private _urlPrefixHumanReadable: string = '';
-  private _port: number = 0;
-  private _routes: { prefix?: string, exact?: string, handler: ServerRouteHandler }[] = [];
-
-  constructor() {
-    this._server = http.createServer(this._onRequest.bind(this));
-    decorateServer(this._server);
-  }
-
-  server() {
-    return this._server;
-  }
-
-  routePrefix(prefix: string, handler: ServerRouteHandler) {
-    this._routes.push({ prefix, handler });
-  }
-
-  routePath(path: string, handler: ServerRouteHandler) {
-    this._routes.push({ exact: path, handler });
-  }
-
-  port(): number {
-    return this._port;
-  }
-
-  private async _tryStart(port: number | undefined, host: string) {
-    const errorPromise = new ManualPromise();
-    const errorListener = (error: Error) => errorPromise.reject(error);
-    this._server.on('error', errorListener);
-
-    try {
-      this._server.listen(port, host);
-      await Promise.race([
-        new Promise(cb => this._server!.once('listening', cb)),
-        errorPromise,
-      ]);
-    } finally {
-      this._server.removeListener('error', errorListener);
-    }
-  }
-
-  async start(options: { port?: number, preferredPort?: number, host?: string } = {}): Promise<void> {
-    const host = options.host || 'localhost';
-    if (options.preferredPort) {
-      try {
-        await this._tryStart(options.preferredPort, host);
-      } catch (e: any) {
-        if (!e || !e.message || !e.message.includes('EADDRINUSE'))
-          throw e;
-        await this._tryStart(undefined, host);
-      }
-    } else {
-      await this._tryStart(options.port, host);
-    }
-
-    const address = this._server.address();
-    if (typeof address === 'string') {
-      this._urlPrefixPrecise = address;
-      this._urlPrefixHumanReadable = address;
-    } else {
-      this._port = address!.port;
-      const resolvedHost = address!.family === 'IPv4' ? address!.address : `[${address!.address}]`;
-      this._urlPrefixPrecise = `http://${resolvedHost}:${address!.port}`;
-      this._urlPrefixHumanReadable = `http://${host}:${address!.port}`;
-    }
-  }
-
-  async stop() {
-    await new Promise(cb => this._server!.close(cb));
-  }
-
-  urlPrefix(purpose: 'human-readable' | 'precise'): string {
-    return purpose === 'human-readable' ? this._urlPrefixHumanReadable : this._urlPrefixPrecise;
-  }
-
-  serveFile(request: http.IncomingMessage, response: http.ServerResponse, absoluteFilePath: string, headers?: { [name: string]: string }): boolean {
-    try {
-      for (const [name, value] of Object.entries(headers || {}))
-        response.setHeader(name, value);
-      if (request.headers.range)
-        this._serveRangeFile(request, response, absoluteFilePath);
-      else
-        this._serveFile(response, absoluteFilePath);
-      return true;
-    } catch (e) {
-      return false;
-    }
-  }
-
-  _serveFile(response: http.ServerResponse, absoluteFilePath: string) {
-    const content = fs.readFileSync(absoluteFilePath);
-    response.statusCode = 200;
-    const contentType = mime.getType(path.extname(absoluteFilePath)) || 'application/octet-stream';
-    response.setHeader('Content-Type', contentType);
-    response.setHeader('Content-Length', content.byteLength);
-    response.end(content);
-  }
-
-  _serveRangeFile(request: http.IncomingMessage, response: http.ServerResponse, absoluteFilePath: string) {
-    const range = request.headers.range;
-    if (!range || !range.startsWith('bytes=') || range.includes(', ') || [...range].filter(char => char === '-').length !== 1) {
-      response.statusCode = 400;
-      return response.end('Bad request');
-    }
-
-    // Parse the range header: https://datatracker.ietf.org/doc/html/rfc7233#section-2.1
-    const [startStr, endStr] = range.replace(/bytes=/, '').split('-');
-
-    // Both start and end (when passing to fs.createReadStream) and the range header are inclusive and start counting at 0.
-    let start: number;
-    let end: number;
-    const size = fs.statSync(absoluteFilePath).size;
-    if (startStr !== '' && endStr === '') {
-      // No end specified: use the whole file
-      start = +startStr;
-      end = size - 1;
-    } else if (startStr === '' && endStr !== '') {
-      // No start specified: calculate start manually
-      start = size - +endStr;
-      end = size - 1;
-    } else {
-      start = +startStr;
-      end = +endStr;
-    }
-
-    // Handle unavailable range request
-    if (Number.isNaN(start) || Number.isNaN(end) || start >= size || end >= size || start > end) {
-      // Return the 416 Range Not Satisfiable: https://datatracker.ietf.org/doc/html/rfc7233#section-4.4
-      response.writeHead(416, {
-        'Content-Range': `bytes */${size}`
-      });
-      return response.end();
-    }
-
-    // Sending Partial Content: https://datatracker.ietf.org/doc/html/rfc7233#section-4.1
-    response.writeHead(206, {
-      'Content-Range': `bytes ${start}-${end}/${size}`,
-      'Accept-Ranges': 'bytes',
-      'Content-Length': end - start + 1,
-      'Content-Type': mime.getType(path.extname(absoluteFilePath))!,
+export async function startHttpServer(config: { host?: string, port?: number }): Promise<http.Server> {
+  const { host, port } = config;
+  const httpServer = http.createServer();
+  await new Promise<void>((resolve, reject) => {
+    httpServer.on('error', reject);
+    httpServer.listen(port, host, () => {
+      resolve();
+      httpServer.removeListener('error', reject);
     });
-
-    const readable = fs.createReadStream(absoluteFilePath, { start, end });
-    readable.pipe(response);
-  }
-
-  private _onRequest(request: http.IncomingMessage, response: http.ServerResponse) {
-    if (request.method === 'OPTIONS') {
-      response.writeHead(200);
-      response.end();
-      return;
-    }
-
-    request.on('error', () => response.end());
-    try {
-      if (!request.url) {
-        response.end();
-        return;
-      }
-      const url = new URL('http://localhost' + request.url);
-      for (const route of this._routes) {
-        if (route.exact && url.pathname === route.exact) {
-          route.handler(request, response);
-          return;
-        }
-        if (route.prefix && url.pathname.startsWith(route.prefix)) {
-          route.handler(request, response);
-          return;
-        }
-      }
-      response.statusCode = 404;
-      response.end();
-    } catch (e) {
-      response.end();
-    }
-  }
-}
-
-function decorateServer(server: net.Server) {
-  const sockets = new Set<net.Socket>();
-  server.on('connection', socket => {
-    sockets.add(socket);
-    socket.once('close', () => sockets.delete(socket));
   });
-
-  const close = server.close;
-  server.close = (callback?: (err?: Error) => void) => {
-    for (const socket of sockets)
-      socket.destroy();
-    sockets.clear();
-    return close.call(server, callback);
-  };
+  return httpServer;
+}
+
+export function httpAddressToString(address: string | net.AddressInfo | null): string {
+  assert(address, 'Could not bind server socket');
+  if (typeof address === 'string')
+    return address;
+  const resolvedPort = address.port;
+  let resolvedHost = address.family === 'IPv4' ? address.address : `[${address.address}]`;
+  if (resolvedHost === '0.0.0.0' || resolvedHost === '[::]')
+    resolvedHost = 'localhost';
+  return `http://${resolvedHost}:${resolvedPort}`;
 }

src/index.ts

@@ -14,10 +14,11 @@
  * limitations under the License.
  */
 
-import { createMCPServer } from './connection.js';
+import { BrowserServerBackend } from './browserServerBackend.js';
 import { resolveConfig } from './config.js';
 import { contextFactory } from './browserContextFactory.js';
-import { filteredTools } from './tools.js';
+import * as mcpServer from './mcp/server.js';
+
 import type { Config } from '../config.js';
 import type { BrowserContext } from 'playwright';
 import type { BrowserContextFactory } from './browserContextFactory.js';
@@ -26,7 +27,7 @@ import type { Server } from '@modelcontextprotocol/sdk/server/index.js';
 export async function createConnection(userConfig: Config = {}, contextGetter?: () => Promise<BrowserContext>): Promise<Server> {
   const config = await resolveConfig(userConfig);
   const factory = contextGetter ? new SimpleBrowserContextFactory(contextGetter) : contextFactory(config.browser);
-  return createMCPServer(config, filteredTools(config), factory);
+  return mcpServer.createServer(new BrowserServerBackend(config, factory));
 }
 
 class SimpleBrowserContextFactory implements BrowserContextFactory {

src/loop/onetool.ts

@@ -21,64 +21,64 @@ import { z } from 'zod';
 import { Client } from '@modelcontextprotocol/sdk/client/index.js';
 import { StdioClientTransport } from '@modelcontextprotocol/sdk/client/stdio.js';
 
-import { FullConfig } from '../config.js';
-import { defineTool } from '../tools/tool.js';
-import { Server } from '../server.js';
-import { startHttpServer, startHttpTransport, startStdioTransport } from '../transport.js';
 import { OpenAIDelegate } from './loopOpenAI.js';
 import { runTask } from './loop.js';
+import { packageJSON } from '../package.js';
+import * as mcpTransport from '../mcp/transport.js';
 
-dotenv.config();
+import type { FullConfig } from '../config.js';
+import type { ServerBackend } from '../mcp/server.js';
+import type * as mcpServer from '../mcp/server.js';
 
 const __filename = url.fileURLToPath(import.meta.url);
 
-let innerClient: Client | undefined;
 const delegate = new OpenAIDelegate();
 
-const oneTool = defineTool({
-  capability: 'core',
-
-  schema: {
-    name: 'browser',
-    title: 'Perform a task with the browser',
-    description: 'Perform a task with the browser. It can click, type, export, capture screenshot, drag, hover, select options, etc.',
-    inputSchema: z.object({
-      task: z.string().describe('The task to perform with the browser'),
-    }),
-    type: 'readOnly',
-  },
-
-  handle: async (context, params, response) => {
-    const result = await runTask(delegate!, innerClient!, params.task);
-    response.addResult(result);
-  },
-});
+const oneToolSchema: mcpServer.ToolSchema<any> = {
+  name: 'browser',
+  title: 'Perform a task with the browser',
+  description: 'Perform a task with the browser. It can click, type, export, capture screenshot, drag, hover, select options, etc.',
+  inputSchema: z.object({
+    task: z.string().describe('The task to perform with the browser'),
+  }),
+  type: 'readOnly',
+};
 
 export async function runOneTool(config: FullConfig) {
-  innerClient = await createInnerClient();
-  const server = new Server(config, [oneTool]);
-  server.setupExitWatchdog();
+  dotenv.config();
+  const serverBackendFactory = () => new OneToolServerBackend();
+  await mcpTransport.start(serverBackendFactory, config.server);
+}
 
-  if (config.server.port !== undefined) {
-    const httpServer = await startHttpServer(config.server);
-    startHttpTransport(httpServer, server);
-  } else {
-    await startStdioTransport(server);
+class OneToolServerBackend implements ServerBackend {
+  readonly name = 'Playwright';
+  readonly version = packageJSON.version;
+  private _innerClient: Client | undefined;
+
+  async initialize() {
+    const transport = new StdioClientTransport({
+      command: 'node',
+      args: [
+        path.resolve(__filename, '../../../cli.js'),
+      ],
+      stderr: 'inherit',
+      env: process.env as Record<string, string>,
+    });
+
+    const client = new Client({ name: 'Playwright Proxy', version: '1.0.0' });
+    await client.connect(transport);
+    await client.ping();
+    this._innerClient = client;
+  }
+
+  tools(): mcpServer.ToolSchema<any>[] {
+    return [oneToolSchema];
+  }
+
+  async callTool(schema: mcpServer.ToolSchema<any>, parsedArguments: any): Promise<mcpServer.ToolResponse> {
+    const result = await runTask(delegate!, this._innerClient!, parsedArguments.task as string);
+    return {
+      content: [{ type: 'text', text: result }],
+    };
   }
 }
-
-async function createInnerClient(): Promise<Client> {
-  const transport = new StdioClientTransport({
-    command: 'node',
-    args: [
-      path.resolve(__filename, '../../../cli.js'),
-    ],
-    stderr: 'inherit',
-    env: process.env as Record<string, string>,
-  });
-
-  const client = new Client({ name: 'Playwright Proxy', version: '1.0.0' });
-  await client.connect(transport);
-  await client.ping();
-  return client;
-}

src/mcp/README.md

@@ -0,0 +1 @@
+- Generic MCP utils, no dependencies on Playwright here.

src/mcp/server.ts

@@ -0,0 +1,105 @@
+/**
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { z } from 'zod';
+import { Server } from '@modelcontextprotocol/sdk/server/index.js';
+import { CallToolRequestSchema, ListToolsRequestSchema } from '@modelcontextprotocol/sdk/types.js';
+import { zodToJsonSchema } from 'zod-to-json-schema';
+
+import type { ImageContent, Implementation, TextContent } from '@modelcontextprotocol/sdk/types.js';
+import type { Transport } from '@modelcontextprotocol/sdk/shared/transport.js';
+
+export type ClientVersion = Implementation;
+
+export type ToolResponse = {
+  content: (TextContent | ImageContent)[];
+  isError?: boolean;
+};
+
+export type ToolSchema<Input extends z.Schema> = {
+  name: string;
+  title: string;
+  description: string;
+  inputSchema: Input;
+  type: 'readOnly' | 'destructive';
+};
+
+export type ToolHandler = (toolName: string, params: any) => Promise<ToolResponse>;
+
+export interface ServerBackend {
+  name: string;
+  version: string;
+  initialize?(): Promise<void>;
+  tools(): ToolSchema<any>[];
+  callTool(schema: ToolSchema<any>, parsedArguments: any): Promise<ToolResponse>;
+  serverInitialized?(version: ClientVersion | undefined): void;
+  serverClosed?(): void;
+}
+
+export type ServerBackendFactory = () => ServerBackend;
+
+export async function connect(serverBackendFactory: ServerBackendFactory, transport: Transport) {
+  const backend = serverBackendFactory();
+  await backend.initialize?.();
+  const server = createServer(backend);
+  await server.connect(transport);
+}
+
+export function createServer(backend: ServerBackend): Server {
+  const server = new Server({ name: backend.name, version: backend.version }, {
+    capabilities: {
+      tools: {},
+    }
+  });
+
+  const tools = backend.tools();
+  server.setRequestHandler(ListToolsRequestSchema, async () => {
+    return { tools: tools.map(tool => ({
+      name: tool.name,
+      description: tool.description,
+      inputSchema: zodToJsonSchema(tool.inputSchema),
+      annotations: {
+        title: tool.title,
+        readOnlyHint: tool.type === 'readOnly',
+        destructiveHint: tool.type === 'destructive',
+        openWorldHint: true,
+      },
+    })) };
+  });
+
+  server.setRequestHandler(CallToolRequestSchema, async request => {
+    const errorResult = (...messages: string[]) => ({
+      content: [{ type: 'text', text: messages.join('\n') }],
+      isError: true,
+    });
+    const tool = tools.find(tool => tool.name === request.params.name) as ToolSchema<any>;
+    if (!tool)
+      return errorResult(`Tool "${request.params.name}" not found`);
+
+    try {
+      return await backend.callTool(tool, tool.inputSchema.parse(request.params.arguments || {}));
+    } catch (error) {
+      return errorResult(String(error));
+    }
+  });
+
+  if (backend.serverInitialized)
+    server.oninitialized = () => backend.serverInitialized!(server.getClientVersion());
+  if (backend.serverClosed)
+    server.onclose = () => backend.serverClosed!();
+
+  return server;
+}

src/mcp/transport.ts

@@ -14,25 +14,34 @@
  * limitations under the License.
  */
 
-import http from 'node:http';
-import assert from 'node:assert';
-import crypto from 'node:crypto';
-
+import http from 'http';
+import crypto from 'crypto';
 import debug from 'debug';
+
 import { SSEServerTransport } from '@modelcontextprotocol/sdk/server/sse.js';
 import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
 import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
+import { httpAddressToString, startHttpServer } from '../httpServer.js';
+import * as mcpServer from './server.js';
 
-import type { AddressInfo } from 'node:net';
-import type { Server } from './server.js';
+import type { ServerBackendFactory } from './server.js';
 
-export async function startStdioTransport(server: Server) {
-  await server.createConnection(new StdioServerTransport());
+export async function start(serverBackendFactory: ServerBackendFactory, options: { host?: string; port?: number }) {
+  if (options.port !== undefined) {
+    const httpServer = await startHttpServer(options);
+    startHttpTransport(httpServer, serverBackendFactory);
+  } else {
+    await startStdioTransport(serverBackendFactory);
+  }
+}
+
+async function startStdioTransport(serverBackendFactory: ServerBackendFactory) {
+  await mcpServer.connect(serverBackendFactory, new StdioServerTransport());
 }
 
 const testDebug = debug('pw:mcp:test');
 
-async function handleSSE(server: Server, req: http.IncomingMessage, res: http.ServerResponse, url: URL, sessions: Map<string, SSEServerTransport>) {
+async function handleSSE(serverBackendFactory: ServerBackendFactory, req: http.IncomingMessage, res: http.ServerResponse, url: URL, sessions: Map<string, SSEServerTransport>) {
   if (req.method === 'POST') {
     const sessionId = url.searchParams.get('sessionId');
     if (!sessionId) {
@@ -51,7 +60,7 @@ async function handleSSE(server: Server, req: http.IncomingMessage, res: http.Se
     const transport = new SSEServerTransport('/sse', res);
     sessions.set(transport.sessionId, transport);
     testDebug(`create SSE session: ${transport.sessionId}`);
-    await server.createConnection(transport);
+    await mcpServer.connect(serverBackendFactory, transport);
     res.on('close', () => {
       testDebug(`delete SSE session: ${transport.sessionId}`);
       sessions.delete(transport.sessionId);
@@ -63,7 +72,7 @@ async function handleSSE(server: Server, req: http.IncomingMessage, res: http.Se
   res.end('Method not allowed');
 }
 
-async function handleStreamable(server: Server, req: http.IncomingMessage, res: http.ServerResponse, sessions: Map<string, StreamableHTTPServerTransport>) {
+async function handleStreamable(serverBackendFactory: ServerBackendFactory, req: http.IncomingMessage, res: http.ServerResponse, sessions: Map<string, StreamableHTTPServerTransport>) {
   const sessionId = req.headers['mcp-session-id'] as string | undefined;
   if (sessionId) {
     const transport = sessions.get(sessionId);
@@ -80,7 +89,7 @@ async function handleStreamable(server: Server, req: http.IncomingMessage, res:
       sessionIdGenerator: () => crypto.randomUUID(),
       onsessioninitialized: async sessionId => {
         testDebug(`create http session: ${transport.sessionId}`);
-        await server.createConnection(transport);
+        await mcpServer.connect(serverBackendFactory, transport);
         sessions.set(sessionId, transport);
       }
     });
@@ -100,28 +109,15 @@ async function handleStreamable(server: Server, req: http.IncomingMessage, res:
   res.end('Invalid request');
 }
 
-export async function startHttpServer(config: { host?: string, port?: number }): Promise<http.Server> {
-  const { host, port } = config;
-  const httpServer = http.createServer();
-  await new Promise<void>((resolve, reject) => {
-    httpServer.on('error', reject);
-    httpServer.listen(port, host, () => {
-      resolve();
-      httpServer.removeListener('error', reject);
-    });
-  });
-  return httpServer;
-}
-
-export function startHttpTransport(httpServer: http.Server, mcpServer: Server) {
+function startHttpTransport(httpServer: http.Server, serverBackendFactory: ServerBackendFactory) {
   const sseSessions = new Map();
   const streamableSessions = new Map();
   httpServer.on('request', async (req, res) => {
     const url = new URL(`http://localhost${req.url}`);
     if (url.pathname.startsWith('/sse'))
-      await handleSSE(mcpServer, req, res, url, sseSessions);
+      await handleSSE(serverBackendFactory, req, res, url, sseSessions);
     else
-      await handleStreamable(mcpServer, req, res, streamableSessions);
+      await handleStreamable(serverBackendFactory, req, res, streamableSessions);
   });
   const url = httpAddressToString(httpServer.address());
   const message = [
@@ -139,14 +135,3 @@ export function startHttpTransport(httpServer: http.Server, mcpServer: Server) {
     // eslint-disable-next-line no-console
   console.error(message);
 }
-
-export function httpAddressToString(address: string | AddressInfo | null): string {
-  assert(address, 'Could not bind server socket');
-  if (typeof address === 'string')
-    return address;
-  const resolvedPort = address.port;
-  let resolvedHost = address.family === 'IPv4' ? address.address : `[${address.address}]`;
-  if (resolvedHost === '0.0.0.0' || resolvedHost === '[::]')
-    resolvedHost = 'localhost';
-  return `http://${resolvedHost}:${resolvedPort}`;
-}

src/program.ts

@@ -18,12 +18,13 @@ import { program, Option } from 'commander';
 // @ts-ignore
 import { startTraceViewerServer } from 'playwright-core/lib/server';
 
-import { startHttpServer, startHttpTransport, startStdioTransport } from './transport.js';
+import * as mcpTransport from './mcp/transport.js';
 import { commaSeparatedList, resolveCLIConfig, semicolonSeparatedList } from './config.js';
-import { Server } from './server.js';
 import { packageJSON } from './package.js';
 import { runWithExtension } from './extension/main.js';
-import { filteredTools } from './tools.js';
+import { BrowserServerBackend } from './browserServerBackend.js';
+import { Context } from './context.js';
+import { contextFactory } from './browserContextFactory.js';
 
 program
     .version('Version ' + packageJSON.version)
@@ -56,6 +57,8 @@ program
     .addOption(new Option('--extension', 'Connect to a running browser instance (Edge/Chrome only). Requires the "Playwright MCP Bridge" browser extension to be installed.').hideHelp())
     .addOption(new Option('--vision', 'Legacy option, use --caps=vision instead').hideHelp())
     .action(async options => {
+      setupExitWatchdog();
+
       if (options.vision) {
         // eslint-disable-next-line no-console
         console.error('The --vision option is deprecated, use --caps=vision instead');
@@ -68,15 +71,9 @@ program
         return;
       }
 
-      const server = new Server(config, filteredTools(config));
-      server.setupExitWatchdog();
-
-      if (config.server.port !== undefined) {
-        const httpServer = await startHttpServer(config.server);
-        startHttpTransport(httpServer, server);
-      } else {
-        await startStdioTransport(server);
-      }
+      const browserContextFactory = contextFactory(config.browser);
+      const serverBackendFactory = () => new BrowserServerBackend(config, browserContextFactory);
+      await mcpTransport.start(serverBackendFactory, config.server);
 
       if (config.saveTrace) {
         const server = await startTraceViewerServer();
@@ -87,4 +84,20 @@ program
       }
     });
 
+function setupExitWatchdog() {
+  let isExiting = false;
+  const handleExit = async () => {
+    if (isExiting)
+      return;
+    isExiting = true;
+    setTimeout(() => process.exit(0), 15000);
+    await Context.disposeAll();
+    process.exit(0);
+  };
+
+  process.stdin.on('close', handleExit);
+  process.on('SIGINT', handleExit);
+  process.on('SIGTERM', handleExit);
+}
+
 void program.parseAsync(process.argv);

src/server.ts

@@ -1,59 +0,0 @@
-/**
- * Copyright (c) Microsoft Corporation.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-import { createMCPServer } from './connection.js';
-import { Context } from './context.js';
-import { contextFactory as defaultContextFactory } from './browserContextFactory.js';
-
-import type { FullConfig } from './config.js';
-import type { Transport } from '@modelcontextprotocol/sdk/shared/transport.js';
-import type { BrowserContextFactory } from './browserContextFactory.js';
-import type { Tool } from './tools/tool.js';
-
-export class Server {
-  readonly config: FullConfig;
-  private _browserConfig: FullConfig['browser'];
-  private _contextFactory: BrowserContextFactory;
-  readonly tools: Tool<any>[];
-
-  constructor(config: FullConfig, tools: Tool<any>[], contextFactory?: BrowserContextFactory) {
-    this.config = config;
-    this.tools = tools;
-    this._browserConfig = config.browser;
-    this._contextFactory = contextFactory ?? defaultContextFactory(this._browserConfig);
-  }
-
-  async createConnection(transport: Transport): Promise<void> {
-    const server = await createMCPServer(this.config, this.tools, this._contextFactory);
-    await server.connect(transport);
-  }
-
-  setupExitWatchdog() {
-    let isExiting = false;
-    const handleExit = async () => {
-      if (isExiting)
-        return;
-      isExiting = true;
-      setTimeout(() => process.exit(0), 15000);
-      await Context.disposeAll();
-      process.exit(0);
-    };
-
-    process.stdin.on('close', handleExit);
-    process.on('SIGINT', handleExit);
-    process.on('SIGTERM', handleExit);
-  }
-}