websockify was formerly named wsproxy and was part of the
[noVNC](https://github.com/kanaka/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.
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.
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.
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](https://github.com/kanaka/websockify/wiki/websock.js)
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.
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