Support HTTP/2

middleware.js

@@ -57,16 +57,24 @@ function createEventStream(heartbeat) {
   }, heartbeat).unref();
   return {
     handler: function(req, res) {
-      req.socket.setKeepAlive(true);
-      res.writeHead(200, {
+      var headers = {
         'Access-Control-Allow-Origin': '*',
         'Content-Type': 'text/event-stream;charset=utf-8',
         'Cache-Control': 'no-cache, no-transform',
-        'Connection': 'keep-alive',
         // While behind nginx, event stream should not be buffered:
         // http://nginx.org/docs/http/ngx_http_proxy_module.html#proxy_buffering
         'X-Accel-Buffering': 'no'
-      });
+      };
+
+      var isHttp1 = !(parseInt(req.httpVersion) >= 2);
+      if (isHttp1) {
+        req.socket.setKeepAlive(true);
+        Object.assign(headers, {
+          'Connection': 'keep-alive',
+        });
+      }
+
+      res.writeHead(200, headers);
       res.write('\n');
       var id = clientId++;
       clients[id] = res;

test/middleware-test.js

@@ -183,6 +183,16 @@ describe("middleware", function() {
           }
         });
     });
+    // Express HTTP/2 support is in progress: https://github.com/expressjs/express/pull/3390
+    it("should not contain `conntection: keep-alive` header for HTTP/2 request");
+    it("should contain `conntection: keep-alive` header for HTTP/1 request", function(done) {
+      request('/__webpack_hmr')
+        .end(function(err, res) {
+          if (err) return done(err);			
+          assert.equal(res.headers['connection'], 'keep-alive');
+          done();
+        });
+    });
   });
 
   beforeEach(function() {