Websockify is a WebSocket to TCP proxy/bridge. This allows a browser to connect to any application/server/service. Implementations in Python, C, Node.js and Ruby.
Python JavaScript C HTML Ruby Clojure Other
Latest commit 30942f1 Jan 19, 2017 @CendioOssman CendioOssman Close connection after Websocket handshake
Otherwise we might misinterpret trailing binary data as a second
HTTP request. This happens when we return from the handler with
data still queued up in the socket.


websockify: WebSockets support for any application/server

websockify was formerly named wsproxy and was part of the noVNC project.

At the most basic level, websockify just translates WebSockets traffic to normal socket traffic. Websockify accepts the WebSockets handshake, parses it, and then begins forwarding traffic between the client and the target in both directions.


Notable commits, announcements and news are posted to @noVNC

If you are a websockify developer/integrator/user (or want to be) please join the noVNC/websockify discussion group

Bugs and feature requests can be submitted via github issues.

If you want to show appreciation for websockify you could donate to a great non-profits such as: Compassion International, SIL, Habitat for Humanity, Electronic Frontier Foundation, Against Malaria Foundation, Nothing But Nets, etc. Please tweet @noVNC if you do.

WebSockets binary data

Starting with websockify 0.5.0, only the HyBi / IETF 6455 WebSocket protocol is supported.

Websockify negotiates whether to base64 encode traffic to and from the client via the subprotocol header (Sec-WebSocket-Protocol). The valid subprotocol values are 'binary' and 'base64' and if the client sends both then the server (the python implementation) will prefer 'binary'. The 'binary' subprotocol indicates that the data will be sent raw using binary WebSocket frames. Some HyBi clients (such as the Flash fallback and older Chrome and iOS versions) do not support binary data which is why the negotiation is necessary.

Encrypted WebSocket connections (wss://)

To encrypt the traffic using the WebSocket 'wss://' URI scheme you need to generate a certificate and key for Websockify to load. By default, Websockify loads a certificate file name self.pem but the --cert=CERT and --key=KEY options can override the file name. You can generate a self-signed certificate using openssl. When asked for the common name, use the hostname of the server where the proxy will be running:

openssl req -new -x509 -days 365 -nodes -out self.pem -keyout self.pem

For a self-signed certificate to work, you need to make your client/browser understand it. You can do this by installing it as accepted certificate, or by using that same certificate for a HTTPS connection to which you navigate first and approve. Browsers generally don't give you the "trust certificate?" prompt by opening a WSS socket with invalid certificate, hence you need to have it acccept it by either of those two methods.

If you have a commercial/valid SSL certificate with one ore more intermediate certificates, concat them into one file, server certificate first, then the intermediate(s) from the CA, etc. Point to this file with the --cert option and then also to the key with --key. Finally, use --ssl-only as needed.

Websock Javascript library

The include/websock.js Javascript library library provides a Websock object that is similar to the standard WebSocket object but Websock enables communication with raw TCP sockets (i.e. the binary stream) via websockify. This is accomplished by base64 encoding the data stream between Websock and websockify.

Websock has built-in receive queue buffering; the message event does not contain actual data but is simply a notification that there is new data available. Several rQ* methods are available to read binary data off of the receive queue.

The Websock API is documented on the websock.js API wiki page

See the "Wrap a Program" section below for an example of using Websock and websockify as a browser telnet client (wstelnet.html).

Additional websockify features

These are not necessary for the basic operation.

  • Daemonizing: When the -D option is specified, websockify runs in the background as a daemon process.

  • SSL (the wss:// WebSockets URI): This is detected automatically by websockify by sniffing the first byte sent from the client and then wrapping the socket if the data starts with '\x16' or '\x80' (indicating SSL).

  • Flash security policy: websockify detects flash security policy requests (again by sniffing the first packet) and answers with an appropriate flash security policy response (and then closes the port). This means no separate flash security policy server is needed for supporting the flash WebSockets fallback emulator.

  • Session recording: This feature that allows recording of the traffic sent and received from the client to a file using the --record option.

  • Mini-webserver: websockify can detect and respond to normal web requests on the same port as the WebSockets proxy and Flash security policy. This functionality is activated with the --web DIR option where DIR is the root of the web directory to serve.

  • Wrap a program: see the "Wrap a Program" section below.

  • Log files: websockify can save all logging information in a file. This functionality is activated with the --log-file FILE option where FILE is the file where the logs should be saved.

Implementations of websockify

The primary implementation of websockify is in python. There are several alternate implementations in other languages (C, Node.js, Clojure, Ruby) in the other/ subdirectory (with varying levels of functionality).

In addition there are several other external projects that implement the websockify "protocol". See the alternate implementation Feature Matrix for more information.

Wrap a Program

In addition to proxying from a source address to a target address (which may be on a different system), websockify has the ability to launch a program on the local system and proxy WebSockets traffic to a normal TCP port owned/bound by the program.

The is accomplished with a small LD_PRELOAD library (rebind.so) which intercepts bind() system calls by the program. The specified port is moved to a new localhost/loopback free high port. websockify then proxies WebSockets traffic directed to the original port to the new (moved) port of the program.

The program wrap mode is invoked by replacing the target with -- followed by the program command line to wrap.

`./run 2023 -- PROGRAM ARGS`

The --wrap-mode option can be used to indicate what action to take when the wrapped program exits or daemonizes.

Here is an example of using websockify to wrap the vncserver command (which backgrounds itself) for use with noVNC:

`./run 5901 --wrap-mode=ignore -- vncserver -geometry 1024x768 :1`

Here is an example of wrapping telnetd (from krb5-telnetd). telnetd exits after the connection closes so the wrap mode is set to respawn the command:

`sudo ./run 2023 --wrap-mode=respawn -- telnetd -debug 2023`

The wstelnet.html page demonstrates a simple WebSockets based telnet client (use 'localhost' and '2023' for the host and port respectively).

Building the Python ssl module (for python 2.5 and older)

  • Install the build dependencies. On Ubuntu use this command:

    sudo aptitude install python-dev bluetooth-dev

  • At the top level of the websockify repostory, download, build and symlink the ssl module:

    wget --no-check-certificate http://pypi.python.org/packages/source/s/ssl/ssl-1.15.tar.gz

    tar xvzf ssl-1.15.tar.gz

    cd ssl-1.15


    cd ../

    ln -sf ssl-1.15/build/lib.linux-*/ssl ssl