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## websockify: WebSockets support for any application/server
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websockify was formerly named wsproxy and was part of the
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[noVNC](https://github.com/kanaka/noVNC) project.
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At the most basic level, websockify just translates WebSockets traffic
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to normal socket traffic. Websockify accepts the WebSockets handshake,
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parses it, and then begins forwarding traffic between the client and
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the target in both directions.
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### WebSockets binary data
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Websockify supports all versions of the WebSockets protocol (Hixie and
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HyBi). The older Hixie versions of the protocol only support UTF-8
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text payloads. In order to transport binary data over UTF-8 an
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encoding must used to encapsulate the data within UTF-8.
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With Hixie clients, Websockify uses base64 to encode all traffic to
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and from the client. This does not affect the data between websockify
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With HyBi clients, websockify negotiates whether to base64 encode
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traffic to and from the client via the subprotocol header
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(Sec-WebSocket-Protocol). The valid subprotocol values are 'binary'
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and 'base64' and if the client sends both then the server (the python
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implementation) will prefer 'binary'. The 'binary' subprotocol
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indicates that the data will be sent raw using binary WebSocket
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frames. Some HyBi clients (such as the Flash fallback and older Chrome
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and iOS versions) do not support binary data which is why the
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negotiation is necessary.
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### Encrypted WebSocket connections (wss://)
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To encrypt the traffic using the WebSocket 'wss://' URI scheme you
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need to generate a certificate for websockify to load. By default websockify
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loads a certificate file name `self.pem` but the `--cert=CERT` option can
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override the file name. You can generate a self-signed certificate using
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openssl. When asked for the common name, use the hostname of the server where
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the proxy will be running:
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openssl req -new -x509 -days 365 -nodes -out self.pem -keyout self.pem
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### Websock Javascript library
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The `include/websock.js` Javascript library library provides a Websock
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object that is similar to the standard WebSocket object but Websock
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enables communication with raw TCP sockets (i.e. the binary stream)
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via websockify. This is accomplished by base64 encoding the data
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stream between Websock and websockify.
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Websock has built-in receive queue buffering; the message event
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does not contain actual data but is simply a notification that
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there is new data available. Several rQ* methods are available to
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read binary data off of the receive queue.
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The Websock API is documented on the [websock.js API wiki page](https://github.com/kanaka/websockify/wiki/websock.js)
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See the "Wrap a Program" section below for an example of using Websock
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and websockify as a browser telnet client (`wstelnet.html`).
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### Additional websockify features
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These are not necessary for the basic operation.
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* Daemonizing: When the `-D` option is specified, websockify runs
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in the background as a daemon process.
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* SSL (the wss:// WebSockets URI): This is detected automatically by
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websockify by sniffing the first byte sent from the client and then
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wrapping the socket if the data starts with '\x16' or '\x80'
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* Flash security policy: websockify detects flash security policy
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requests (again by sniffing the first packet) and answers with an
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appropriate flash security policy response (and then closes the
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port). This means no separate flash security policy server is needed
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for supporting the flash WebSockets fallback emulator.
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* Session recording: This feature that allows recording of the traffic
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sent and received from the client to a file using the `--record`
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* Mini-webserver: websockify can detect and respond to normal web
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requests on the same port as the WebSockets proxy and Flash security
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policy. This functionality is activate with the `--web DIR` option
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where DIR is the root of the web directory to serve.
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* Wrap a program: see the "Wrap a Program" section below.
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### Implementations of websockify
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The primary implementation of websockify is in python. There are
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several alternate implementations in other languages (C, Node.js,
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Clojure, Ruby) in the `other/` subdirectory (with varying levels of
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In addition there are several other external projects that implement
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the websockify "protocol". See the alternate implementation [Feature
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Matrix](https://github.com/kanaka/websockify/wiki/Feature_Matrix) for
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In addition to proxying from a source address to a target address
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(which may be on a different system), websockify has the ability to
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launch a program on the local system and proxy WebSockets traffic to
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a normal TCP port owned/bound by the program.
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The is accomplished with a small LD_PRELOAD library (`rebind.so`)
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which intercepts bind() system calls by the program. The specified
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port is moved to a new localhost/loopback free high port. websockify
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then proxies WebSockets traffic directed to the original port to the
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new (moved) port of the program.
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The program wrap mode is invoked by replacing the target with `--`
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followed by the program command line to wrap.
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`./websockify 2023 -- PROGRAM ARGS`
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The `--wrap-mode` option can be used to indicate what action to take
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when the wrapped program exits or daemonizes.
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Here is an example of using websockify to wrap the vncserver command
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(which backgrounds itself) for use with
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[noVNC](https://github.com/kanaka/noVNC):
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`./websockify 5901 --wrap-mode=ignore -- vncserver -geometry 1024x768 :1`
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Here is an example of wrapping telnetd (from krb5-telnetd).telnetd
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exits after the connection closes so the wrap mode is set to respawn
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`sudo ./websockify 2023 --wrap-mode=respawn -- telnetd -debug 2023`
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The `wstelnet.html` page demonstrates a simple WebSockets based telnet
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### Building the Python ssl module (for python 2.5 and older)
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* Install the build dependencies. On Ubuntu use this command:
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`sudo aptitude install python-dev bluetooth-dev`
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* Download, build the ssl module and symlink to it:
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`wget http://pypi.python.org/packages/source/s/ssl/ssl-1.15.tar.gz`
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`tar xvzf ssl-1.15.tar.gz`
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`ln -sf ssl-1.15/build/lib.linux-*/ssl ssl`
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README.md
