WebSocketHandler¶

class services.handler.WebSocketHandler(application, request, **kwargs)¶

Bases: tornado.websocket.WebSocketHandler

WebSockethanlder base class

Parameters:	{Tornado WebSocket} -- tornado base (tornado) –

Attributes Summary

SUPPORTED_METHODS
cookies	An alias for self.request.cookies <.httputil.HTTPServerRequest.cookies>.
current_user	The authenticated user for this request.
locale	The locale for the current session.
max_message_size	Maximum allowed message size.
path_args
path_kwargs
ping_interval	The interval for websocket keep-alive pings.
ping_timeout	If no ping is received in this many seconds, close the websocket connection (VPNs, etc.
selected_subprotocol	The subprotocol returned by select_subprotocol.
settings	An alias for self.application.settings <Application.settings>.
stream
xsrf_token	The XSRF-prevention token for the current user/session.

Methods Summary

add_header(name, value, str, …)	Adds the given response header and value.
check_etag_header()	Checks the Etag header against requests’s If-None-Match.
check_origin(origin)	Override to enable support for allowing alternate origins.
check_xsrf_cookie()	Verifies that the _xsrf cookie matches the _xsrf argument.
clear()	Resets all headers and content for this response.
clear_all_cookies(path, domain)	Deletes all the cookies the user sent with this request.
clear_cookie(name, path, domain)	Deletes the cookie with the given name.
clear_header(name)	Clears an outgoing header, undoing a previous set_header call.
close(code, reason)	Closes this Web Socket.
compute_etag()	Computes the etag header to be used for this request.
create_signed_value(name, value, bytes], version)	Signs and timestamps a string so it cannot be forged.
create_template_loader(template_path)	Returns a new template loader for the given path.
data_received(chunk)	Implement this method to handle streamed request data.
decode_argument(value, name)	Decodes an argument from the request.
delete(*args, **kwargs)
detach()	Take control of the underlying stream.
finish(chunk, bytes, dict] = None)	Finishes this response, ending the HTTP request.
flush(include_footers)	Flushes the current output buffer to the network.
get(*args, **kwargs)
get_argument(name, default, str, …)	Returns the value of the argument with the given name.
get_arguments(name, strip)	Returns a list of the arguments with the given name.
get_body_argument(name, default, str, …)	Returns the value of the argument with the given name from the request body.
get_body_arguments(name, strip)	Returns a list of the body arguments with the given name.
get_browser_locale(default)	Determines the user’s locale from Accept-Language header.
get_compression_options()	Override to return compression options for the connection.
get_cookie(name, default)	Returns the value of the request cookie with the given name.
get_current_user()	Override to determine the current user from, e.g., a cookie.
get_login_url()	Override to customize the login URL based on the request.
get_query_argument(name, default, str, …)	Returns the value of the argument with the given name from the request query string.
get_query_arguments(name, strip)	Returns a list of the query arguments with the given name.
get_secure_cookie(name, value, max_age_days, …)	Returns the given signed cookie if it validates, or None.
get_secure_cookie_key_version(name, value)	Returns the signing key version of the secure cookie.
get_status()	Returns the status code for our response.
get_template_namespace()	Returns a dictionary to be used as the default template namespace.
get_template_path()	Override to customize template path for each handler.
get_user_locale()	Override to determine the locale from the authenticated user.
get_websocket_protocol()
head(*args, **kwargs)
initialize(_callback, _service)	Basic initialize call
log_exception(typ, NoneType], value, …)	Override to customize logging of uncaught exceptions.
on_close()	Default close protocoll websocket
on_connection_close()	Called in async handlers if the client closed the connection.
on_finish()	Called after the end of a request.
on_message(message)	Handle incoming messages on the WebSocket
on_ping(data)	Invoked when the a ping frame is received.
on_pong(data)	Invoked when the response to a ping frame is received.
on_ws_connection_close(close_code, close_reason)
open(*args, **kwargs)	Default open protocoll websocket
options(*args, **kwargs)
patch(*args, **kwargs)
ping(data, bytes] = b)	Send ping frame to the remote end.
post(*args, **kwargs)
prepare()	Called at the beginning of a request before get/post/etc.
put(*args, **kwargs)
redirect(url, permanent, status)	Sends a redirect to the given (optionally relative) URL.
render(template_name, **kwargs)	Renders the template with the given arguments as the response.
render_embed_css(css_embed)	Default method used to render the final embedded css for the rendered webpage.
render_embed_js(js_embed)	Default method used to render the final embedded js for the rendered webpage.
render_linked_css(css_files)	Default method used to render the final css links for the rendered webpage.
render_linked_js(js_files)	Default method used to render the final js links for the rendered webpage.
render_string(template_name, **kwargs)	Generate the given template with the given arguments.
require_setting(name, feature)	Raises an exception if the given app setting is not defined.
reverse_url(name, *args)	Alias for Application.reverse_url.
select_subprotocol(subprotocols)	Override to implement subprotocol negotiation.
send_error(*args, **kwargs)	Sends the given HTTP error code to the browser.
set_cookie(name, value, bytes], domain, …)	Sets an outgoing cookie name/value with the given options.
set_default_headers()	Override this to set HTTP headers at the beginning of the request.
set_etag_header()	Sets the response’s Etag header using self.compute_etag().
set_header(name, value, str, …)	Sets the given response header name and value.
set_nodelay(value)	Set the no-delay flag for this stream.
set_secure_cookie(name, value, bytes], …)	Signs and timestamps a cookie so it cannot be forged.
set_status(status_code, reason)	Sets the status code for our response.
static_url(path, include_host, **kwargs)	Returns a static URL for the given relative static file path.
write(chunk, bytes, dict])	Writes the given chunk to the output buffer.
write_error(status_code, **kwargs)	Override to implement custom error pages.
write_message(message, str, typing.Dict[str, …)	Sends the given message to the client of this Web Socket.
xsrf_form_html()	An HTML <input/> element to be included with all POST forms.

Attributes Documentation

SUPPORTED_METHODS = ('GET', 'HEAD', 'POST', 'DELETE', 'PATCH', 'PUT', 'OPTIONS')¶

cookies¶

An alias for self.request.cookies <.httputil.HTTPServerRequest.cookies>.

current_user¶

The authenticated user for this request.

This is set in one of two ways:

• A subclass may override get_current_user(), which will be called automatically the first time self.current_user is accessed. get_current_user() will only be called once per request, and is cached for future access:

  def get_current_user(self):
      user_cookie = self.get_secure_cookie("user")
      if user_cookie:
          return json.loads(user_cookie)
      return None
  

• It may be set as a normal variable, typically from an overridden prepare():

  @gen.coroutine
  def prepare(self):
      user_id_cookie = self.get_secure_cookie("user_id")
      if user_id_cookie:
          self.current_user = yield load_user(user_id_cookie)
  

Note that prepare() may be a coroutine while get_current_user() may not, so the latter form is necessary if loading the user requires asynchronous operations.

The user object may be any type of the application’s choosing.

locale¶

The locale for the current session.

Determined by either get_user_locale, which you can override to set the locale based on, e.g., a user preference stored in a database, or get_browser_locale, which uses the Accept-Language header.

max_message_size¶

Maximum allowed message size.

If the remote peer sends a message larger than this, the connection will be closed.

Default is 10MiB.

path_args = None¶

path_kwargs = None¶

ping_interval¶

The interval for websocket keep-alive pings.

Set websocket_ping_interval = 0 to disable pings.

ping_timeout¶

If no ping is received in this many seconds, close the websocket connection (VPNs, etc. can fail to cleanly close ws connections). Default is max of 3 pings or 30 seconds.

selected_subprotocol¶

The subprotocol returned by select_subprotocol.

New in version 5.1.

settings¶

An alias for self.application.settings <Application.settings>.

stream = None¶

xsrf_token¶

The XSRF-prevention token for the current user/session.

To prevent cross-site request forgery, we set an ‘_xsrf’ cookie and include the same ‘_xsrf’ value as an argument with all POST requests. If the two do not match, we reject the form submission as a potential forgery.

See http://en.wikipedia.org/wiki/Cross-site_request_forgery

This property is of type bytes, but it contains only ASCII characters. If a character string is required, there is no need to base64-encode it; just decode the byte string as UTF-8.

Changed in version 3.2.2: The xsrf token will now be have a random mask applied in every request, which makes it safe to include the token in pages that are compressed. See http://breachattack.com for more information on the issue fixed by this change. Old (version 1) cookies will be converted to version 2 when this method is called unless the xsrf_cookie_version Application setting is set to 1.

Changed in version 4.3: The xsrf_cookie_kwargs Application setting may be used to supply additional cookie options (which will be passed directly to set_cookie). For example, xsrf_cookie_kwargs=dict(httponly=True, secure=True) will set the secure and httponly flags on the _xsrf cookie.

Methods Documentation

add_header(name: str, value: Union[bytes, str, numbers.Integral, datetime.datetime]) → None¶

Adds the given response header and value.

Unlike set_header, add_header may be called multiple times to return multiple values for the same header.

check_etag_header() → bool¶

Checks the Etag header against requests’s If-None-Match.

Returns True if the request’s Etag matches and a 304 should be returned. For example:

self.set_etag_header()
if self.check_etag_header():
    self.set_status(304)
    return

This method is called automatically when the request is finished, but may be called earlier for applications that override compute_etag and want to do an early check for If-None-Match before completing the request. The Etag header should be set (perhaps with set_etag_header) before calling this method.

check_origin(origin)¶

Override to enable support for allowing alternate origins.

The origin argument is the value of the Origin HTTP header, the url responsible for initiating this request. This method is not called for clients that do not send this header; such requests are always allowed (because all browsers that implement WebSockets support this header, and non-browser clients do not have the same cross-site security concerns).

Should return True to accept the request or False to reject it. By default, rejects all requests with an origin on a host other than this one.

This is a security protection against cross site scripting attacks on browsers, since WebSockets are allowed to bypass the usual same-origin policies and don’t use CORS headers.

Warning

This is an important security measure; don’t disable it without understanding the security implications. In particular, if your authentication is cookie-based, you must either restrict the origins allowed by check_origin() or implement your own XSRF-like protection for websocket connections. See these articles for more.

To accept all cross-origin traffic (which was the default prior to Tornado 4.0), simply override this method to always return True:

def check_origin(self, origin):
    return True

To allow connections from any subdomain of your site, you might do something like:

def check_origin(self, origin):
    parsed_origin = urllib.parse.urlparse(origin)
    return parsed_origin.netloc.endswith(".mydomain.com")

New in version 4.0.

check_xsrf_cookie() → None¶

Verifies that the _xsrf cookie matches the _xsrf argument.

To prevent cross-site request forgery, we set an _xsrf cookie and include the same value as a non-cookie field with all POST requests. If the two do not match, we reject the form submission as a potential forgery.

The _xsrf value may be set as either a form field named _xsrf or in a custom HTTP header named X-XSRFToken or X-CSRFToken (the latter is accepted for compatibility with Django).

See http://en.wikipedia.org/wiki/Cross-site_request_forgery

Changed in version 3.2.2: Added support for cookie version 2. Both versions 1 and 2 are supported.

clear() → None¶

Resets all headers and content for this response.

clear_all_cookies(path: str = '/', domain: str = None) → None¶

Deletes all the cookies the user sent with this request.

See clear_cookie for more information on the path and domain parameters.

Similar to set_cookie, the effect of this method will not be seen until the following request.

Changed in version 3.2: Added the path and domain parameters.

clear_cookie(name: str, path: str = '/', domain: str = None) → None¶

Deletes the cookie with the given name.

Due to limitations of the cookie protocol, you must pass the same path and domain to clear a cookie as were used when that cookie was set (but there is no way to find out on the server side which values were used for a given cookie).

Similar to set_cookie, the effect of this method will not be seen until the following request.

clear_header(name: str) → None¶

Clears an outgoing header, undoing a previous set_header call.

Note that this method does not apply to multi-valued headers set by add_header.

close(code: int = None, reason: str = None) → None¶

Closes this Web Socket.

Once the close handshake is successful the socket will be closed.

code may be a numeric status code, taken from the values defined in RFC 6455 section 7.4.1. reason may be a textual message about why the connection is closing. These values are made available to the client, but are not otherwise interpreted by the websocket protocol.

Changed in version 4.0: Added the code and reason arguments.

compute_etag() → Union[str, NoneType]¶

Computes the etag header to be used for this request.

By default uses a hash of the content written so far.

May be overridden to provide custom etag implementations, or may return None to disable tornado’s default etag support.

create_signed_value(name: str, value: Union[str, bytes], version: int = None) → bytes¶

Signs and timestamps a string so it cannot be forged.

Normally used via set_secure_cookie, but provided as a separate method for non-cookie uses. To decode a value not stored as a cookie use the optional value argument to get_secure_cookie.

Changed in version 3.2.1: Added the version argument. Introduced cookie version 2 and made it the default.

create_template_loader(template_path: str) → tornado.template.BaseLoader¶

Returns a new template loader for the given path.

May be overridden by subclasses. By default returns a directory-based loader on the given path, using the autoescape and template_whitespace application settings. If a template_loader application setting is supplied, uses that instead.

data_received(chunk: bytes) → Union[typing.Awaitable[NoneType], NoneType]¶

Implement this method to handle streamed request data.

Requires the .stream_request_body decorator.

May be a coroutine for flow control.

decode_argument(value: bytes, name: str = None) → str¶

Decodes an argument from the request.

The argument has been percent-decoded and is now a byte string. By default, this method decodes the argument as utf-8 and returns a unicode string, but this may be overridden in subclasses.

This method is used as a filter for both get_argument() and for values extracted from the url and passed to get()/post()/etc.

The name of the argument is provided if known, but may be None (e.g. for unnamed groups in the url regex).

delete(*args, **kwargs) → None¶

detach() → tornado.iostream.IOStream¶

Take control of the underlying stream.

Returns the underlying .IOStream object and stops all further HTTP processing. Intended for implementing protocols like websockets that tunnel over an HTTP handshake.

This method is only supported when HTTP/1.1 is used.

New in version 5.1.

finish(chunk: Union[str, bytes, dict] = None) → Future[None]¶

Finishes this response, ending the HTTP request.

Passing a chunk to finish() is equivalent to passing that chunk to write() and then calling finish() with no arguments.

Returns a .Future which may optionally be awaited to track the sending of the response to the client. This .Future resolves when all the response data has been sent, and raises an error if the connection is closed before all data can be sent.

Changed in version 5.1: Now returns a .Future instead of None.

flush(include_footers: bool = False) → Future[None]¶

Flushes the current output buffer to the network.

The callback argument, if given, can be used for flow control: it will be run when all flushed data has been written to the socket. Note that only one flush callback can be outstanding at a time; if another flush occurs before the previous flush’s callback has been run, the previous callback will be discarded.

Changed in version 4.0: Now returns a .Future if no callback is given.

Changed in version 6.0: The callback argument was removed.

get(*args, **kwargs) → None¶

get_argument(name: str, default: Union[NoneType, str, tornado.web._ArgDefaultMarker] = <tornado.web._ArgDefaultMarker object>, strip: bool = True) → Union[str, NoneType]¶

Returns the value of the argument with the given name.

If default is not provided, the argument is considered to be required, and we raise a MissingArgumentError if it is missing.

If the argument appears in the request more than once, we return the last value.

This method searches both the query and body arguments.

get_arguments(name: str, strip: bool = True) → List[str]¶

Returns a list of the arguments with the given name.

If the argument is not present, returns an empty list.

This method searches both the query and body arguments.

get_body_argument(name: str, default: Union[NoneType, str, tornado.web._ArgDefaultMarker] = <tornado.web._ArgDefaultMarker object>, strip: bool = True) → Union[str, NoneType]¶

Returns the value of the argument with the given name from the request body.

If default is not provided, the argument is considered to be required, and we raise a MissingArgumentError if it is missing.

If the argument appears in the url more than once, we return the last value.

New in version 3.2.

get_body_arguments(name: str, strip: bool = True) → List[str]¶

Returns a list of the body arguments with the given name.

If the argument is not present, returns an empty list.

New in version 3.2.

get_browser_locale(default: str = 'en_US') → tornado.locale.Locale¶

Determines the user’s locale from Accept-Language header.

See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.4

get_compression_options() → Union[typing.Dict[str, typing.Any], NoneType]¶

Override to return compression options for the connection.

If this method returns None (the default), compression will be disabled. If it returns a dict (even an empty one), it will be enabled. The contents of the dict may be used to control the following compression options:

compression_level specifies the compression level.

mem_level specifies the amount of memory used for the internal compression state.

These parameters are documented in details here: https://docs.python.org/3.6/library/zlib.html#zlib.compressobj

New in version 4.1.

Changed in version 4.5: Added compression_level and mem_level.

get_cookie(name: str, default: str = None) → Union[str, NoneType]¶

Returns the value of the request cookie with the given name.

If the named cookie is not present, returns default.

This method only returns cookies that were present in the request. It does not see the outgoing cookies set by set_cookie in this handler.

get_current_user() → Any¶

Override to determine the current user from, e.g., a cookie.

This method may not be a coroutine.

get_login_url() → str¶

Override to customize the login URL based on the request.

By default, we use the login_url application setting.

get_query_argument(name: str, default: Union[NoneType, str, tornado.web._ArgDefaultMarker] = <tornado.web._ArgDefaultMarker object>, strip: bool = True) → Union[str, NoneType]¶

Returns the value of the argument with the given name from the request query string.

If default is not provided, the argument is considered to be required, and we raise a MissingArgumentError if it is missing.

If the argument appears in the url more than once, we return the last value.

New in version 3.2.

get_query_arguments(name: str, strip: bool = True) → List[str]¶

Returns a list of the query arguments with the given name.

If the argument is not present, returns an empty list.

New in version 3.2.

get_secure_cookie(name: str, value: str = None, max_age_days: int = 31, min_version: int = None) → Union[bytes, NoneType]¶

Returns the given signed cookie if it validates, or None.

The decoded cookie value is returned as a byte string (unlike get_cookie).

Similar to get_cookie, this method only returns cookies that were present in the request. It does not see outgoing cookies set by set_secure_cookie in this handler.

Changed in version 3.2.1: Added the min_version argument. Introduced cookie version 2; both versions 1 and 2 are accepted by default.

get_secure_cookie_key_version(name: str, value: str = None) → Union[int, NoneType]¶

Returns the signing key version of the secure cookie.

The version is returned as int.

get_status() → int¶

Returns the status code for our response.

get_template_namespace() → Dict[str, Any]¶

Returns a dictionary to be used as the default template namespace.

May be overridden by subclasses to add or modify values.

The results of this method will be combined with additional defaults in the tornado.template module and keyword arguments to render or render_string.

get_template_path() → Union[str, NoneType]¶

Override to customize template path for each handler.

By default, we use the template_path application setting. Return None to load templates relative to the calling file.

get_user_locale() → Union[tornado.locale.Locale, NoneType]¶

Override to determine the locale from the authenticated user.

If None is returned, we fall back to get_browser_locale().

This method should return a tornado.locale.Locale object, most likely obtained via a call like tornado.locale.get("en")

get_websocket_protocol() → Union[_ForwardRef('WebSocketProtocol'), NoneType]¶

head(*args, **kwargs) → None¶

initialize(_callback, _service)¶

Basic initialize call

Parameters:	{CallBack func} -- Callback for received data (_callback) –

log_exception(typ: Union[typing.Type[BaseException], NoneType], value: Union[BaseException, NoneType], tb: Union[traceback, NoneType]) → None¶

Override to customize logging of uncaught exceptions.

By default logs instances of HTTPError as warnings without stack traces (on the tornado.general logger), and all other exceptions as errors with stack traces (on the tornado.application logger).

New in version 3.1.

on_close()¶

Default close protocoll websocket

on_connection_close() → None¶

Called in async handlers if the client closed the connection.

Override this to clean up resources associated with long-lived connections. Note that this method is called only if the connection was closed during asynchronous processing; if you need to do cleanup after every request override on_finish instead.

Proxies may keep a connection open for a time (perhaps indefinitely) after the client has gone away, so this method may not be called promptly after the end user closes their connection.

on_finish() → None¶

Called after the end of a request.

Override this method to perform cleanup, logging, etc. This method is a counterpart to prepare. on_finish may not produce any output, as it is called after the response has been sent to the client.

on_message(message)¶

Handle incoming messages on the WebSocket

This method must be overridden.

Changed in version 4.5: on_message can be a coroutine.

on_ping(data: bytes) → None¶

Invoked when the a ping frame is received.

on_pong(data: bytes) → None¶

Invoked when the response to a ping frame is received.

on_ws_connection_close(close_code: int = None, close_reason: str = None) → None¶

open(*args, **kwargs)¶

Default open protocoll websocket

options(*args, **kwargs) → None¶

patch(*args, **kwargs) → None¶

ping(data: Union[str, bytes] = b'') → None¶

Send ping frame to the remote end.

The data argument allows a small amount of data (up to 125 bytes) to be sent as a part of the ping message. Note that not all websocket implementations expose this data to applications.

Consider using the websocket_ping_interval application setting instead of sending pings manually.

Changed in version 5.1: The data argument is now optional.

post(*args, **kwargs) → None¶

prepare() → Union[typing.Awaitable[NoneType], NoneType]¶

Called at the beginning of a request before get/post/etc.

Override this method to perform common initialization regardless of the request method.

Asynchronous support: Use async def or decorate this method with .gen.coroutine to make it asynchronous. If this method returns an Awaitable execution will not proceed until the Awaitable is done.

New in version 3.1: Asynchronous support.

put(*args, **kwargs) → None¶

redirect(url: str, permanent: bool = False, status: int = None) → None¶

Sends a redirect to the given (optionally relative) URL.

If the status argument is specified, that value is used as the HTTP status code; otherwise either 301 (permanent) or 302 (temporary) is chosen based on the permanent argument. The default is 302 (temporary).

render(template_name: str, **kwargs) → Future[None]¶

Renders the template with the given arguments as the response.

render() calls finish(), so no other output methods can be called after it.

Returns a .Future with the same semantics as the one returned by finish. Awaiting this .Future is optional.

Changed in version 5.1: Now returns a .Future instead of None.

render_embed_css(css_embed: Iterable[bytes]) → bytes¶

Default method used to render the final embedded css for the rendered webpage.

Override this method in a sub-classed controller to change the output.

render_embed_js(js_embed: Iterable[bytes]) → bytes¶

Default method used to render the final embedded js for the rendered webpage.

Override this method in a sub-classed controller to change the output.

render_linked_css(css_files: Iterable[str]) → str¶

Default method used to render the final css links for the rendered webpage.

Override this method in a sub-classed controller to change the output.

render_linked_js(js_files: Iterable[str]) → str¶

Default method used to render the final js links for the rendered webpage.

Override this method in a sub-classed controller to change the output.

render_string(template_name: str, **kwargs) → bytes¶

Generate the given template with the given arguments.

We return the generated byte string (in utf8). To generate and write a template as a response, use render() above.

require_setting(name: str, feature: str = 'this feature') → None¶

Raises an exception if the given app setting is not defined.

reverse_url(name: str, *args) → str¶

Alias for Application.reverse_url.

select_subprotocol(subprotocols: List[str]) → Union[str, NoneType]¶

Override to implement subprotocol negotiation.

subprotocols is a list of strings identifying the subprotocols proposed by the client. This method may be overridden to return one of those strings to select it, or None to not select a subprotocol.

Failure to select a subprotocol does not automatically abort the connection, although clients may close the connection if none of their proposed subprotocols was selected.

The list may be empty, in which case this method must return None. This method is always called exactly once even if no subprotocols were proposed so that the handler can be advised of this fact.

Changed in version 5.1: Previously, this method was called with a list containing an empty string instead of an empty list if no subprotocols were proposed by the client.

send_error(*args, **kwargs) → None¶

Sends the given HTTP error code to the browser.

If flush() has already been called, it is not possible to send an error, so this method will simply terminate the response. If output has been written but not yet flushed, it will be discarded and replaced with the error page.

Override write_error() to customize the error page that is returned. Additional keyword arguments are passed through to write_error.

set_cookie(name: str, value: Union[str, bytes], domain: str = None, expires: Union[float, typing.Tuple, datetime.datetime] = None, path: str = '/', expires_days: int = None, **kwargs) → None¶

Sets an outgoing cookie name/value with the given options.

Newly-set cookies are not immediately visible via get_cookie; they are not present until the next request.

expires may be a numeric timestamp as returned by time.time, a time tuple as returned by time.gmtime, or a datetime.datetime object.

Additional keyword arguments are set on the cookies.Morsel directly. See https://docs.python.org/3/library/http.cookies.html#http.cookies.Morsel for available attributes.

set_default_headers() → None¶

Override this to set HTTP headers at the beginning of the request.

For example, this is the place to set a custom Server header. Note that setting such headers in the normal flow of request processing may not do what you want, since headers may be reset during error handling.

set_etag_header() → None¶

Sets the response’s Etag header using self.compute_etag().

Note: no header will be set if compute_etag() returns None.

This method is called automatically when the request is finished.

set_header(name: str, value: Union[bytes, str, numbers.Integral, datetime.datetime]) → None¶

Sets the given response header name and value.

All header values are converted to strings (datetime objects are formatted according to the HTTP specification for the Date header).

set_nodelay(value: bool) → None¶

Set the no-delay flag for this stream.

By default, small messages may be delayed and/or combined to minimize the number of packets sent. This can sometimes cause 200-500ms delays due to the interaction between Nagle’s algorithm and TCP delayed ACKs. To reduce this delay (at the expense of possibly increasing bandwidth usage), call self.set_nodelay(True) once the websocket connection is established.

See .BaseIOStream.set_nodelay for additional details.

New in version 3.1.

set_secure_cookie(name: str, value: Union[str, bytes], expires_days: int = 30, version: int = None, **kwargs) → None¶

Signs and timestamps a cookie so it cannot be forged.

You must specify the cookie_secret setting in your Application to use this method. It should be a long, random sequence of bytes to be used as the HMAC secret for the signature.

To read a cookie set with this method, use get_secure_cookie().

Note that the expires_days parameter sets the lifetime of the cookie in the browser, but is independent of the max_age_days parameter to get_secure_cookie.

Secure cookies may contain arbitrary byte values, not just unicode strings (unlike regular cookies)

Similar to set_cookie, the effect of this method will not be seen until the following request.

Changed in version 3.2.1: Added the version argument. Introduced cookie version 2 and made it the default.

set_status(status_code: int, reason: str = None) → None¶

Sets the status code for our response.

Parameters:	status_code (int) – Response status code. reason (str) – Human-readable reason phrase describing the status code. If None, it will be filled in from http.client.responses or “Unknown”.

Changed in version 5.0: No longer validates that the response code is in http.client.responses.

static_url(path: str, include_host: bool = None, **kwargs) → str¶

Returns a static URL for the given relative static file path.

This method requires you set the static_path setting in your application (which specifies the root directory of your static files).

This method returns a versioned url (by default appending ?v=<signature>), which allows the static files to be cached indefinitely. This can be disabled by passing include_version=False (in the default implementation; other static file implementations are not required to support this, but they may support other options).

By default this method returns URLs relative to the current host, but if include_host is true the URL returned will be absolute. If this handler has an include_host attribute, that value will be used as the default for all static_url calls that do not pass include_host as a keyword argument.

write(chunk: Union[str, bytes, dict]) → None¶

Writes the given chunk to the output buffer.

To write the output to the network, use the flush() method below.

If the given chunk is a dictionary, we write it as JSON and set the Content-Type of the response to be application/json. (if you want to send JSON as a different Content-Type, call set_header after calling write()).

Note that lists are not converted to JSON because of a potential cross-site security vulnerability. All JSON output should be wrapped in a dictionary. More details at http://haacked.com/archive/2009/06/25/json-hijacking.aspx/ and https://github.com/facebook/tornado/issues/1009

write_error(status_code: int, **kwargs) → None¶

Override to implement custom error pages.

write_error may call write, render, set_header, etc to produce output as usual.

If this error was caused by an uncaught exception (including HTTPError), an exc_info triple will be available as kwargs["exc_info"]. Note that this exception may not be the “current” exception for purposes of methods like sys.exc_info() or traceback.format_exc.

write_message(message: Union[bytes, str, typing.Dict[str, typing.Any]], binary: bool = False) → Future[None]¶

Sends the given message to the client of this Web Socket.

The message may be either a string or a dict (which will be encoded as json). If the binary argument is false, the message will be sent as utf8; in binary mode any byte string is allowed.

If the connection is already closed, raises WebSocketClosedError. Returns a .Future which can be used for flow control.

Changed in version 3.2: WebSocketClosedError was added (previously a closed connection would raise an AttributeError)

Changed in version 4.3: Returns a .Future which can be used for flow control.

Changed in version 5.0: Consistently raises WebSocketClosedError. Previously could sometimes raise .StreamClosedError.

xsrf_form_html() → str¶

An HTML <input/> element to be included with all POST forms.

It defines the _xsrf input value, which we check on all POST requests to prevent cross-site request forgery. If you have set the xsrf_cookies application setting, you must include this HTML within all of your HTML forms.

In a template, this method should be called with {% module xsrf_form_html() %}

See check_xsrf_cookie() above for more information.