websockify - WebSockets to TCP socket bridge
websockify [options] [source_addr:]source_port target_addr:target_port
websockify [options] [source_addr:]source_port -- WRAP_COMMAND_LINE
-h, --help show this help message and exit
-v, --verbose verbose messages and per frame traffic
--record=FILE record sessions to FILE.[session_number]
-D, --daemon become a daemon (background process)
--run-once handle a single WebSocket connection and exit
--timeout=TIMEOUT after TIMEOUT seconds exit when not connected
--cert=CERT SSL certificate file
--key=KEY SSL key file (if separate from cert)
--ssl-only disallow non-encrypted connections
--web=DIR run webserver on same port. Serve files from DIR.
--wrap-mode=MODE action to take when the wrapped program exits or
daemonizes: exit (default), ignore, respawn
At the most basic level, websockify just translates WebSockets traffic
to normal TCP socket traffic. Websockify accepts the WebSockets
handshake, parses it, and then begins forwarding traffic between the
client and the target in both directions.
websockify was formerly named wsproxy and was part of the noVNC
WebSockets binary data
Websockify supports all versions of the WebSockets protocol (Hixie and
HyBI). The older Hixie versions of the protocol only support UTF-8 text
payloads. In order to transport binary data over UTF-8 an encoding must
used to encapsulate the data within UTF-8. Websockify uses base64 to
encode all traffic to and from the client. This does not affect the
data between websockify and the server.
Encrypted WebSocket connections (wss://)
To encrypt the traffic using the WebSocket 'wss://' URI scheme you need
to generate a certificate for websockify to load. By default websockify
loads a certificate file name self.pem but the --cert=CERT option 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
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
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.php).
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 '' or
'€' (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
* 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 activate 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.
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.
`./websockify 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:
`./websockify 5901 --wrap-mode=ignore -- vncserver -geometry 1024x768
Here is an example of wrapping telnetd (from krb5-telnetd).telnetd
exits after the connection closes so the wrap mode is set to respawn
`sudo ./websockify 2023 --wrap-mode=respawn -- telnetd -debug 2023`
The wstelnet.php page demonstrates a simple WebSockets based telnet
Joel Martin (firstname.lastname@example.org)