chore: isolate SSE client browsers (#76)

src/program.ts

@@ -25,8 +25,8 @@ import { SSEServerTransport } from '@modelcontextprotocol/sdk/server/sse.js';
 
 
 import { createServer } from './index';
+import { ServerList } from './server';
 
-import type { Server } from '@modelcontextprotocol/sdk/server/index.js';
 import type { LaunchOptions } from 'playwright';
 import assert from 'assert';
 
@@ -44,86 +44,33 @@ program
         headless: !!options.headless,
         channel: 'chrome',
       };
-      const server = createServer({
-        userDataDir: options.userDataDir ?? await userDataDir(),
+      const userDataDir = options.userDataDir ?? await createUserDataDir();
+      const serverList = new ServerList(() => createServer({
+        userDataDir,
         launchOptions,
         vision: !!options.vision,
-      });
-      setupExitWatchdog(server);
+      }));
+      setupExitWatchdog(serverList);
 
       if (options.port) {
-        const sessions = new Map<string, SSEServerTransport>();
-        const httpServer = http.createServer(async (req, res) => {
-          if (req.method === 'POST') {
-            const host = req.headers.host ?? 'http://unknown';
-            const sessionId = new URL(host + req.url!).searchParams.get('sessionId');
-            if (!sessionId) {
-              res.statusCode = 400;
-              res.end('Missing sessionId');
-              return;
-            }
-            const transport = sessions.get(sessionId);
-            if (!transport) {
-              res.statusCode = 404;
-              res.end('Session not found');
-              return;
-            }
-
-            await transport.handlePostMessage(req, res);
-            return;
-          } else if (req.method === 'GET') {
-            const transport = new SSEServerTransport('/sse', res);
-            sessions.set(transport.sessionId, transport);
-            res.on('close', () => {
-              sessions.delete(transport.sessionId);
-            });
-            await server.connect(transport);
-            return;
-          } else {
-            res.statusCode = 405;
-            res.end('Method not allowed');
-          }
-        });
-        httpServer.listen(+options.port, () => {
-          const address = httpServer.address();
-          assert(address, 'Could not bind server socket');
-          let urlPrefixHumanReadable: string;
-          if (typeof address === 'string') {
-            urlPrefixHumanReadable = address;
-          } else {
-            const port = address.port;
-            let resolvedHost = address.family === 'IPv4' ? address.address : `[${address.address}]`;
-            if (resolvedHost === '0.0.0.0' || resolvedHost === '[::]')
-              resolvedHost = 'localhost';
-            urlPrefixHumanReadable = `http://${resolvedHost}:${port}`;
-          }
-          console.log(`Listening on ${urlPrefixHumanReadable}`);
-          console.log('Put this in your client config:');
-          console.log(JSON.stringify({
-            'mcpServers': {
-              'playwright': {
-                'url': `${urlPrefixHumanReadable}/sse`
-              }
-            }
-          }, undefined, 2));
-        });
+        startSSEServer(+options.port, serverList);
       } else {
-        const transport = new StdioServerTransport();
-        await server.connect(transport);
+        const server = await serverList.create();
+        await server.connect(new StdioServerTransport());
       }
     });
 
-function setupExitWatchdog(server: Server) {
+function setupExitWatchdog(serverList: ServerList) {
   process.stdin.on('close', async () => {
     setTimeout(() => process.exit(0), 15000);
-    await server.close();
+    await serverList.closeAll();
     process.exit(0);
   });
 }
 
 program.parse(process.argv);
 
-async function userDataDir() {
+async function createUserDataDir() {
   let cacheDirectory: string;
   if (process.platform === 'linux')
     cacheDirectory = process.env.XDG_CACHE_HOME || path.join(os.homedir(), '.cache');
@@ -137,3 +84,64 @@ async function userDataDir() {
   await fs.promises.mkdir(result, { recursive: true });
   return result;
 }
+
+async function startSSEServer(port: number, serverList: ServerList) {
+  const sessions = new Map<string, SSEServerTransport>();
+  const httpServer = http.createServer(async (req, res) => {
+    if (req.method === 'POST') {
+      const host = req.headers.host ?? 'http://unknown';
+      const sessionId = new URL(host + req.url!).searchParams.get('sessionId');
+      if (!sessionId) {
+        res.statusCode = 400;
+        res.end('Missing sessionId');
+        return;
+      }
+      const transport = sessions.get(sessionId);
+      if (!transport) {
+        res.statusCode = 404;
+        res.end('Session not found');
+        return;
+      }
+
+      await transport.handlePostMessage(req, res);
+      return;
+    } else if (req.method === 'GET') {
+      const transport = new SSEServerTransport('/sse', res);
+      sessions.set(transport.sessionId, transport);
+      const server = await serverList.create();
+      res.on('close', () => {
+        sessions.delete(transport.sessionId);
+        serverList.close(server).catch(e => console.error(e));
+      });
+      await server.connect(transport);
+      return;
+    } else {
+      res.statusCode = 405;
+      res.end('Method not allowed');
+    }
+  });
+
+  httpServer.listen(port, () => {
+    const address = httpServer.address();
+    assert(address, 'Could not bind server socket');
+    let url: string;
+    if (typeof address === 'string') {
+      url = address;
+    } else {
+      const resolvedPort = address.port;
+      let resolvedHost = address.family === 'IPv4' ? address.address : `[${address.address}]`;
+      if (resolvedHost === '0.0.0.0' || resolvedHost === '[::]')
+        resolvedHost = 'localhost';
+      url = `http://${resolvedHost}:${resolvedPort}`;
+    }
+    console.log(`Listening on ${url}`);
+    console.log('Put this in your client config:');
+    console.log(JSON.stringify({
+      'mcpServers': {
+        'playwright': {
+          'url': `${url}/sse`
+        }
+      }
+    }, undefined, 2));
+  });
+}

src/server.ts

@@ -88,3 +88,29 @@ export function createServerWithTools(options: Options): Server {
 
   return server;
 }
+
+export class ServerList {
+  private _servers: Server[] = [];
+  private _serverFactory: () => Server;
+
+  constructor(serverFactory: () => Server) {
+    this._serverFactory = serverFactory;
+  }
+
+  async create() {
+    const server = this._serverFactory();
+    this._servers.push(server);
+    return server;
+  }
+
+  async close(server: Server) {
+    const index = this._servers.indexOf(server);
+    if (index !== -1)
+      this._servers.splice(index, 1);
+    await server.close();
+  }
+
+  async closeAll() {
+    await Promise.all(this._servers.map(server => server.close()));
+  }
+}