feat: support streamable http transport (#243)

Adds support for the new StreamableHttp transport. I'm not aware of any
clients that implement it, but somebody's gotta make the start! Once
some clients support it, we can also advertise it in the README.

src/program.ts

@@ -14,18 +14,13 @@
  * limitations under the License.
  */
 
-import http from 'http';
-
 import { program } from 'commander';
-import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
-import { SSEServerTransport } from '@modelcontextprotocol/sdk/server/sse.js';
-
 
 import { createServer } from './index';
 import { ServerList } from './server';
 
-import assert from 'assert';
 import { ToolCapability } from './tools/tool';
+import { startHttpTransport, startStdioTransport } from './transport';
 
 const packageJSON = require('../package.json');
 
@@ -53,12 +48,10 @@ program
       }));
       setupExitWatchdog(serverList);
 
-      if (options.port) {
-        startSSEServer(+options.port, options.host || 'localhost', serverList);
-      } else {
-        const server = await serverList.create();
-        await server.connect(new StdioServerTransport());
-      }
+      if (options.port)
+        startHttpTransport(+options.port, options.host, serverList);
+      else
+        await startStdioTransport(serverList);
     });
 
 function setupExitWatchdog(serverList: ServerList) {
@@ -74,64 +67,3 @@ function setupExitWatchdog(serverList: ServerList) {
 }
 
 program.parse(process.argv);
-
-function startSSEServer(port: number, host: string, serverList: ServerList) {
-  const sessions = new Map<string, SSEServerTransport>();
-  const httpServer = http.createServer(async (req, res) => {
-    if (req.method === 'POST') {
-      const searchParams = new URL(`http://localhost${req.url}`).searchParams;
-      const sessionId = searchParams.get('sessionId');
-      if (!sessionId) {
-        res.statusCode = 400;
-        res.end('Missing sessionId');
-        return;
-      }
-      const transport = sessions.get(sessionId);
-      if (!transport) {
-        res.statusCode = 404;
-        res.end('Session not found');
-        return;
-      }
-
-      await transport.handlePostMessage(req, res);
-      return;
-    } else if (req.method === 'GET') {
-      const transport = new SSEServerTransport('/sse', res);
-      sessions.set(transport.sessionId, transport);
-      const server = await serverList.create();
-      res.on('close', () => {
-        sessions.delete(transport.sessionId);
-        serverList.close(server).catch(e => console.error(e));
-      });
-      await server.connect(transport);
-      return;
-    } else {
-      res.statusCode = 405;
-      res.end('Method not allowed');
-    }
-  });
-
-  httpServer.listen(port, host, () => {
-    const address = httpServer.address();
-    assert(address, 'Could not bind server socket');
-    let url: string;
-    if (typeof address === 'string') {
-      url = address;
-    } else {
-      const resolvedPort = address.port;
-      let resolvedHost = address.family === 'IPv4' ? address.address : `[${address.address}]`;
-      if (resolvedHost === '0.0.0.0' || resolvedHost === '[::]')
-        resolvedHost = host === 'localhost' ? 'localhost' : resolvedHost;
-      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));
-  });
-}