diff --git a/tests/sshserver.py b/tests/sshserver.py
index 72a6884..ef395bc 100644
--- a/tests/sshserver.py
+++ b/tests/sshserver.py
@@ -65,7 +65,7 @@ class Server(paramiko.ServerInterface):
 
     def check_auth_password(self, username, password):
         print('Auth attempt with username: {!r} & password: {!r}'.format(username, password)) # noqa
-        if (username in ['robey', 'bar']) and (password == 'foo'):
+        if (username in ['robey', 'bar', 'foo']) and (password == 'foo'):
             return paramiko.AUTH_SUCCESSFUL
         return paramiko.AUTH_FAILED
 
@@ -150,6 +150,17 @@ def run_ssh_server(port=2200, running=True):
         if username == 'bar':
             msg = chan.recv(1024)
             chan.send(msg)
+        elif username == 'foo':
+            lst = []
+            while True:
+                msg = chan.recv(32 * 1024)
+                lst.append(msg)
+                if msg.endswith(b'\r\n\r\n'):
+                    break
+            data = b''.join(lst)
+            while data:
+                s = chan.send(data)
+                data = data[s:]
 
         chan.close()
         t.close()
diff --git a/tests/test_app.py b/tests/test_app.py
index 1a827c3..5258191 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -487,4 +487,32 @@ class TestAppInDebug(OtherTestBase):
 
 class TestAppMiscell(OtherTestBase):
 
-    debug = False
+    @tornado.testing.gen_test
+    def test_app_for_sending_message_with_large_size(self):
+        url = self.get_url('/')
+        client = self.get_http_client()
+        body = urlencode(dict(self.body, username='foo'))
+        response = yield client.fetch(url, method='POST', body=body,
+                                      headers=self.headers)
+        data = json.loads(to_str(response.body))
+        self.assertIsNone(data['status'])
+        self.assertIsNotNone(data['id'])
+        self.assertIsNotNone(data['encoding'])
+
+        url = url.replace('http', 'ws')
+        ws_url = url + 'ws?id=' + data['id']
+        ws = yield tornado.websocket.websocket_connect(ws_url)
+        msg = yield ws.read_message()
+        self.assertEqual(to_str(msg, data['encoding']), banner)
+
+        send = 'h' * (64 * 1024) + '\r\n\r\n'
+        yield ws.write_message(json.dumps({'data': send}))
+        lst = []
+        while True:
+            msg = yield ws.read_message()
+            lst.append(msg)
+            if msg.endswith(b'\r\n\r\n'):
+                break
+        recv = b''.join(lst).decode(data['encoding'])
+        self.assertEqual(send, recv)
+        ws.close()
diff --git a/webssh/worker.py b/webssh/worker.py
index a53eb86..5734a5e 100644
--- a/webssh/worker.py
+++ b/webssh/worker.py
@@ -6,7 +6,7 @@ from tornado.iostream import _ERRNO_CONNRESET
 from tornado.util import errno_from_exception
 
 
-BUF_SIZE = 1024
+BUF_SIZE = 32 * 1024
 workers = {}
 
 
@@ -46,6 +46,8 @@ class Worker(object):
         if self.mode != mode:
             self.loop.update_handler(self.fd, mode)
             self.mode = mode
+        if mode == IOLoop.WRITE:
+            self.loop.call_later(0.1, self, self.fd, IOLoop.WRITE)
 
     def on_read(self):
         logging.debug('worker {} on read'.format(self.id))