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https://github.com/vi/websocat

Command-line client for WebSockets, like netcat (or curl) for ws:// with advanced socat-like functions
https://github.com/vi/websocat

cli command-line command-line-tool curl netcat proxy rfc-6455 socat websocket-client websocket-server websockets

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Command-line client for WebSockets, like netcat (or curl) for ws:// with advanced socat-like functions

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README 

        
# websocat

Netcat, curl and socat for [WebSockets](https://en.wikipedia.org/wiki/WebSocket).



[![Gitter](https://badges.gitter.im/websocat.svg)](https://gitter.im/websocat/Lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=body_badge)

[![image-build](https://github.com/vi/websocat/actions/workflows/container-image-buildah.yml/badge.svg)](https://github.com/vi/websocat/pkgs/container/websocat)



## Examples



### Connect to public echo server (Ctrl+d to quit)



```

$ websocat ws://ws.vi-server.org/mirror

123

123

ABC

ABC



$ docker run --rm -ti ghcr.io/vi/websocat:nightly wss://ws.vi-server.org/mirror

123

123

ABC

ABC

```



### Serve and connect



```

A$ websocat -s 1234

Listening on ws://127.0.0.1:1234/

ABC

123



B$ websocat ws://127.0.0.1:1234/

ABC

123

```



### Open a tab in Chromium using remote debugging.



```

$ chromium --remote-debugging-port=9222&

$ curl -sg http://127.0.0.1:9222/json/new | grep webSocketDebuggerUrl | cut -d'"' -f4 | head -1

ws://127.0.0.1:9222/devtools/page/A331E56CCB8615EB4FCB720425A82259

$ echo 'Page.navigate {"url":"https://example.com"}' | websocat -n1 --jsonrpc --jsonrpc-omit-jsonrpc ws://127.0.0.1:9222/devtools/page/A331E56CCB8615EB4FCB720425A82259

{"id":2,"result":{"frameId":"A331E56CCB8615EB4FCB720425A82259","loaderId":"EF5AAD19F2F8BB27FAF55F94FFB27DF9"}}

```



### Proxy TCP connections to WebSocket connections and back.



```

$ websocat --oneshot -b ws-l:127.0.0.1:1234 tcp:127.0.0.1:22&

$ websocat --oneshot -b tcp-l:127.0.0.1:1236 ws://127.0.0.1:1234/&

$ nc 127.0.0.1 1236

SSH-2.0-OpenSSH_7.4p1 Debian-10+deb9u3

qwertyu

Protocol mismatch.

```



### Broadcast all messages between connected WebSocket clients



```

A$ websocat -t ws-l:127.0.0.1:1234 broadcast:mirror:

B$ websocat ws://127.0.0.1:1234

C$ websocat ws://127.0.0.1:1234

```



(if you like this one, you may actually want https://github.com/vi/wsbroad/ instead)



See [moreexamples.md](./moreexamples.md) for further examples.



## Features



* Connecting to and serving WebSockets from command line.

* Executing external program and making it communicate to WebSocket using stdin/stdout.

* Text and binary modes, converting between lines (or null-terminated records) and messages.

* Inetd mode, UNIX sockets (including abstract namespaced on Linux).

* Integration with Nginx using TCP or UNIX sockets.

* Directly using unauthenticated SOCKS5 servers for connecting to WebSockets and listening WebSocket connection.

* Auto-reconnect and connection-reuse modes.

* Linux, Windows and Mac support, with [pre-built executables][releases].

* Low-level WebSocket clients and servers with overridable underlying transport connection, e.g. calling external program to serve as a transport for websocat (for SSL, proxying, etc.).



[releases]:https://github.com/vi/websocat/releases



# Installation



There are multiple options for installing WebSocat. From easy to hard:



## Fedora



[Copr](https://copr.fedorainfracloud.org/coprs/atim/websocat/): `sudo dnf copr enable atim/websocat -y && sudo dnf install websocat`



## FreeBSD



`pkg install websocat`



## Debian / Ubuntu

* Download a pre-build executable from [GitHub releases][releases].

* Websocat is not yet officially packaged for Debian. Some older versions of Websocat may also have Debian package files available on Github releases.



## macOS



[Homebrew](https://brew.sh): `brew install websocat`



[MacPorts](https://www.macports.org): `sudo port install websocat`



## From source

* Install the [Rust toolchain](https://rustup.rs/) and do `cargo install --features=ssl websocat`. If something fails with a `-sys` crate, try without `--features=ssl`;

* Build Websocat from source code (see below), then move `target/release/websocat` somewhere to the PATH.



## Pre-built binaries

Pre-built binaries for Linux (usual and musl), Windows, OS X and Android are available on the [releases page](https://github.com/vi/websocat/releases).



Building from source code

---



1. Install the [Rust toolchain](https://rustup.rs/). Note that Websocat v1 (i.e. the current stable version) may fail to support too new Rust due to its old dependencies which can be broken by e.g. [this](https://github.com/rust-lang/rust/pull/78802).

2. `cargo build --release --features=ssl`.

3. Find the executable somewhere under `target/`, e.g. in `target/release/websocat`.



### Rust versions



|Websocat versions|Minimal Rust version|Maximal Rust version|

|----|----|----|

| 4.0.0-alpha1 | 1.84 | ?   |

| 1.12+     | ?    | ?          |

| 1.9 - 1.11| 1.46 | maybe 1.63 |

| 1.6 - 1.8 | 1.34 | maybe 1.63  |

| 1.3 - 1.5 | 1.31 | 1.47? |

| 1.2       | 1.28 | 1.47? |

| 1.0-1.1   | 1.23 | 1.47? |

| 1.2       | ?    | ?     |



Note that building with legacy Rust version (e.g. 1.46) may require manually copying `Cargo.lock.legacy` to `Cargo.lock` prior to the building.



Early non-async versions of Websocat should be buildable by even older rustc.  



Note that old versions of Websocat may misbehave if built by Rust 1.48 or later due to https://github.com/rust-lang/rust/pull/71274/.



It may be not a good idea to build v1.x line of Websocat with Rust 1.64 due to [IP address representation refactor]. It may expose previously hidden undefined behaviour in legacy dependencies. (In practice, it seems to just work though - but a lot of time passed since I checked Websocat properly and in detail).



[ipaddr]:https://github.com/rust-lang/rust/pull/78802



SSL on Android

---



websocat's `wss://` may fail on Android. As a workaround, download certificate bundle, for example, from https://curl.haxx.se/ca/cacert.pem and specify it explicitly:



    SSL_CERT_FILE=cacert.pem /data/local/tmp/websocat wss://echo.websocket.org



Or just use `--insecure` option.



Documentation

---



Basic usage examples are provided at the top of this README and in `--help` message. More tricks are described in [moreexamples.md](./moreexamples.md).



There is a [list of all address types and overlays](doc.md).



`websocat --help=long` output



```

websocat 1.13.0

Vitaly "_Vi" Shukela 

Command-line client for web sockets, like netcat/curl/socat for ws://.



USAGE:

    websocat ws://URL | wss://URL               (simple client)

    websocat -s port                            (simple server)

    websocat [FLAGS] [OPTIONS]    (advanced mode)



FLAGS:

        --stdout-announce-listening-ports        [A] Print a line to stdout for each port being listened

        --async-stdio

            [A] On UNIX, set stdin and stdout to nonblocking mode instead of spawning a thread. This should improve

            performance, but may break other programs running on the same console.

        --compress-deflate

            [A] Compress data coming to a WebSocket using deflate method. Affects only binary WebSocket messages.



        --compress-gzip

            [A] Compress data coming to a WebSocket using gzip method. Affects only binary WebSocket messages.



        --compress-zlib

            [A] Compress data coming to a WebSocket using zlib method. Affects only binary WebSocket messages.



        --crypto-reverse

            [A] Swap encryption and decryption operations in `crypto:` specifier - encrypt on read, decrypto on write.



        --dump-spec                              [A] Instead of running, dump the specifiers representation to stdout

    -e, --set-environment

            Set WEBSOCAT_* environment variables when doing exec:/cmd:/sh-c:

            Currently it's WEBSOCAT_URI and WEBSOCAT_CLIENT for

            request URI and client address (if TCP)

            Beware of ShellShock or similar security problems.

    -E, --exit-on-eof                            Close a data transfer direction if the other one reached EOF

        --foreachmsg-wait-read                   [A] Wait for reading to finish before closing foreachmsg:'s peer

        --jsonrpc

            Format messages you type as JSON RPC 2.0 method calls. First word becomes method name, the rest becomes

            parameters, possibly automatically wrapped in [].

        --jsonrpc-omit-jsonrpc                   [A] Omit `jsonrpc` field when using `--jsonrpc`, e.g. for Chromium

        --just-generate-key                      [A] Just a Sec-WebSocket-Key value without running main Websocat

        --lengthprefixed-little-endian

            [A] Use little-endian framing headers instead of big-endian for `lengthprefixed:` overlay.



        --lengthprefixed-skip-read-direction

            [A] Only affect one direction of the `lengthprefixed:` overlay, bypass tranformation for the other one.



        --lengthprefixed-skip-write-direction

            [A] Only affect one direction of the `lengthprefixed:` overlay, bypass tranformation for the other one.



        --linemode-strip-newlines

            [A] Don't include trailing \n or \r\n coming from streams in WebSocket messages



    -0, --null-terminated                        Use \0 instead of \n for linemode

        --no-line                                [A] Don't automatically insert line-to-message transformation

        --no-exit-on-zeromsg

            [A] Don't exit when encountered a zero message. Zero messages are used internally in Websocat, so it may

            fail to close connection at all.

        --no-fixups

            [A] Don't perform automatic command-line fixups. May destabilize websocat operation. Use --dump-spec without

            --no-fixups to discover what is being inserted automatically and read the full manual about Websocat

            internal workings.

        --no-async-stdio                         [A] Inhibit using stdin/stdout in a nonblocking way if it is not a tty

    -1, --one-message                            Send and/or receive only one message. Use with --no-close and/or -u/-U.

        --oneshot                                Serve only once. Not to be confused with -1 (--one-message)

        --print-ping-rtts

            Print measured round-trip-time to stderr after each received WebSocket pong.



        --exec-exit-on-disconnect

            [A] Make exec: or sh-c: or cmd: immediately exit when connection is closed, don't wait for termination.



        --exec-sighup-on-stdin-close

            [A] Make exec: or sh-c: or cmd: send SIGHUP on UNIX when input is closed.



        --exec-sighup-on-zero-msg

            [A] Make exec: or sh-c: or cmd: send SIGHUP on UNIX when facing incoming zero-length message.



    -q                                           Suppress all diagnostic messages, except of startup errors

        --reuser-send-zero-msg-on-disconnect

            [A] Make reuse-raw: send a zero-length message to the peer when some clients disconnects.



    -s, --server-mode                            Simple server mode: specify TCP port or addr:port as single argument

    -S, --strict

            strict line/message mode: drop too long messages instead of splitting them, drop incomplete lines.



        --timestamp-monotonic                    [A] Use monotonic clock for `timestamp:` overlay

    -k, --insecure                               Accept invalid certificates and hostnames while connecting to TLS

        --udp-broadcast                          [A] Set SO_BROADCAST

        --udp-multicast-loop                     [A] Set IP[V6]_MULTICAST_LOOP

        --udp-oneshot                            [A] udp-listen: replies only one packet per client

        --udp-reuseaddr

            [A] Set SO_REUSEADDR for UDP socket. Listening TCP sockets are always reuseaddr.



        --uncompress-deflate

            [A] Uncompress data coming from a WebSocket using deflate method. Affects only binary WebSocket messages.



        --uncompress-gzip

            [A] Uncompress data coming from a WebSocket using deflate method. Affects only binary WebSocket messages.



        --uncompress-zlib

            [A] Uncompress data coming from a WebSocket using deflate method. Affects only binary WebSocket messages.



    -u, --unidirectional                         Inhibit copying data in one direction

    -U, --unidirectional-reverse

            Inhibit copying data in the other direction (or maybe in both directions if combined with -u)



        --accept-from-fd

            [A] Do not call `socket(2)` in UNIX socket listener peer, start with `accept(2)` using specified file

            descriptor number as argument instead of filename

        --unlink                                 [A] Unlink listening UNIX socket before binding to it

    -V, --version                                Prints version information

    -v                                           Increase verbosity level to info or further

    -b, --binary                                 Send message to WebSockets as binary messages

    -n, --no-close                               Don't send Close message to websocket on EOF

        --websocket-ignore-zeromsg

            [A] Silently drop incoming zero-length WebSocket messages. They may cause connection close due to usage of

            zero-len message as EOF flag inside Websocat.

    -t, --text                                   Send message to WebSockets as text messages

        --base64

            Encode incoming binary WebSocket messages in one-line Base64 If `--binary-prefix` (see `--help=full`) is

            set, outgoing WebSocket messages that start with the prefix are decoded from base64 prior to sending.

        --base64-text

            [A] Encode incoming text WebSocket messages in one-line Base64. I don't know whether it can be ever useful,

            but it's for symmetry with `--base64`.



OPTIONS:

        --socks5 

            Use specified address:port as a SOCKS5 proxy. Note that proxy authentication is not supported yet. Example:

            --socks5 127.0.0.1:9050

        --autoreconnect-delay-millis 

            [A] Delay before reconnect attempt for `autoreconnect:` overlay. [default: 20]



        --basic-auth 

            Add `Authorization: Basic` HTTP request header with this base64-encoded parameter



        --queue-len 

            [A] Number of pending queued messages for broadcast reuser [default: 16]



    -B, --buffer-size                                   Maximum message size, in bytes [default: 65536]

        --byte-to-exit-on 

            [A] Override the byte which byte_to_exit_on: overlay looks for [default: 28]



        --client-pkcs12-der                       [A] Client identity TLS certificate

        --client-pkcs12-passwd 

            [A] Password for --client-pkcs12-der pkcs12 archive. Required on Mac.



        --close-reason 

            Close connection with a reason message. This option only takes effect if --close-status-code option is

            provided as well.

        --close-status-code                       Close connection with a status code.

        --crypto-key 

            [A] Specify encryption/decryption key for `crypto:` specifier. Requires `base64:`, `file:` or `pwd:` prefix.



    -H, --header ...

            Add custom HTTP header to websocket client request. Separate header name and value with a colon and

            optionally a single space. Can be used multiple times. Note that single -H may eat multiple further

            arguments, leading to confusing errors. Specify headers at the end or with equal sign like -H='X: y'.

        --server-header ...

            Add custom HTTP header to websocket upgrade reply. Separate header name and value with a colon and

            optionally a single space. Can be used multiple times. Note that single -H may eat multiple further

            arguments, leading to confusing errors.

        --exec-args ...

            [A] Arguments for the `exec:` specifier. Must be the last option, everything after it gets into the exec

            args list.

        --header-to-env ...

            Forward specified incoming request header to H_* environment variable for `exec:`-like specifiers.



    -h, --help 

            See the help.

            --help=short is the list of easy options and address types

            --help=long lists all options and types (see [A] markers)

            --help=doc also shows longer description and examples.

        --inhibit-pongs 

            [A] Stop replying to incoming WebSocket pings after specified number of replies



        --just-generate-accept 

            [A] Just a Sec-WebSocket-Accept value based on supplied Sec-WebSocket-Key value without running main

            Websocat

        --lengthprefixed-nbytes 

            [A] Use this number of length header bytes for `lengthprefixed:` overlay. [default: 4]



        --max-messages 

            Maximum number of messages to copy in one direction.



        --max-messages-rev 

            Maximum number of messages to copy in the other direction.



        --conncap 

            Maximum number of simultaneous connections for listening mode



        --max-sent-pings 

            [A] Stop sending pings after this number of sent pings



        --max-ws-frame-length 

            [A] Maximum size of incoming WebSocket frames, to prevent memory overflow [default: 104857600]



        --max-ws-message-length 

            [A] Maximum size of incoming WebSocket messages (sans of one data frame), to prevent memory overflow

            [default: 209715200]

        --origin                                             Add Origin HTTP header to websocket client request

        --pkcs12-der 

            Pkcs12 archive needed to accept SSL connections, certificate and key.

            A command to output it: openssl pkcs12 -export -out output.pkcs12 -inkey key.pem -in cert.pem

            Use with -s (--server-mode) option or with manually specified TLS overlays.

            See moreexamples.md for more info.

        --pkcs12-passwd 

            Password for --pkcs12-der pkcs12 archive. Required on Mac.



    -p, --preamble ...

            Prepend copied data with a specified string. Can be specified multiple times.



    -P, --preamble-reverse ...

            Prepend copied data with a specified string (reverse direction). Can be specified multiple times.



        --prometheus 

            Expose Prometheus metrics on specified IP address and port in addition to running usual Websocat session



        --request-header ...

            [A] Specify HTTP request headers for `http-request:` specifier.



    -X, --request-method                             [A] Method to use for `http-request:` specifier

        --request-uri                                   [A] URI to use for `http-request:` specifier

        --restrict-uri 

            When serving a websocket, only accept the given URI, like `/ws`

            This liberates other URIs for things like serving static files or proxying.

    -F, --static-file ...

            Serve a named static file for non-websocket connections.

            Argument syntax: ::

            Argument example: /index.html:text/html:index.html

            Directories are not and will not be supported for security reasons.

            Can be specified multiple times. Recommended to specify them at the end or with equal sign like `-F=...`,

            otherwise this option may eat positional arguments

        --socks5-bind-script 

            [A] Execute specified script in `socks5-bind:` mode when remote port number becomes known.



        --socks5-destination 

            [A] Examples: 1.2.3.4:5678  2600:::80  hostname:5678



        --tls-domain 

            [A] Specify domain for SNI or certificate verification when using tls-connect: overlay



        --udp-multicast ...

            [A] Issue IP[V6]_ADD_MEMBERSHIP for specified multicast address. Can be specified multiple times.



        --udp-multicast-iface-v4 ...

            [A] IPv4 address of multicast network interface. Has to be either not specified or specified the same number

            of times as multicast IPv4 addresses. Order matters.

        --udp-multicast-iface-v6 ...

            [A] Index of network interface for IPv6 multicast. Has to be either not specified or specified the same

            number of times as multicast IPv6 addresses. Order matters.

        --udp-ttl                                           [A] Set IP_TTL, also IP_MULTICAST_TTL if applicable

        --protocol 

            Specify this Sec-WebSocket-Protocol: header when connecting



        --server-protocol 

            Force this Sec-WebSocket-Protocol: header when accepting a connection



        --websocket-version                       Override the Sec-WebSocket-Version value

        --binary-prefix 

            [A] Prepend specified text to each received WebSocket binary message. Also strip this prefix from outgoing

            messages, explicitly marking them as binary even if `--text` is specified

        --ws-c-uri 

            [A] URI to use for ws-c: overlay [default: ws://0.0.0.0/]



        --ping-interval                            Send WebSocket pings each this number of seconds

        --ping-timeout 

            Drop WebSocket connection if Pong message not received for this number of seconds



        --text-prefix 

            [A] Prepend specified text to each received WebSocket text message. Also strip this prefix from outgoing

            messages, explicitly marking them as text even if `--binary` is specified



ARGS:

        In simple mode, WebSocket URL to connect. In advanced mode first address (there are many kinds of

               addresses) to use. See --help=types for info about address types. If this is an address for

               listening, it will try serving multiple connections.

        In advanced mode, second address to connect. If this is an address for listening, it will accept only

               one connection.



Basic examples:

  Command-line websocket client:

    websocat ws://ws.vi-server.org/mirror/

    

  WebSocket server

    websocat -s 8080

    

  WebSocket-to-TCP proxy:

    websocat --binary ws-l:127.0.0.1:8080 tcp:127.0.0.1:5678

    



Full list of address types:

	ws://           	Insecure (ws://) WebSocket client. Argument is host and URL.

	wss://          	Secure (wss://) WebSocket client. Argument is host and URL.

	ws-listen:      	WebSocket server. Argument is host and port to listen.

	inetd-ws:       	WebSocket inetd server. [A]

	l-ws-unix:      	WebSocket UNIX socket-based server. [A]

	l-ws-abstract:  	WebSocket abstract-namespaced UNIX socket server. [A]

	ws-lowlevel-client:	[A] Low-level HTTP-independent WebSocket client connection without associated HTTP upgrade.

	ws-lowlevel-server:	[A] Low-level HTTP-independent WebSocket server connection without associated HTTP upgrade.

	wss-listen:     	Listen for secure WebSocket connections on a TCP port

	http:           	[A] Issue HTTP request, receive a 1xx or 2xx reply, then pass

	asyncstdio:     	[A] Set stdin and stdout to nonblocking mode, then use it as a communication counterpart. UNIX-only.

	inetd:          	Like `asyncstdio:`, but intended for inetd(8) usage. [A]

	tcp:            	Connect to specified TCP host and port. Argument is a socket address.

	tcp-listen:     	Listen TCP port on specified address.

	ssl-listen:     	Listen for SSL connections on a TCP port

	sh-c:           	Start specified command line using `sh -c` (even on Windows)

	cmd:            	Start specified command line using `sh -c` or `cmd /C` (depending on platform)

	exec:           	Execute a program directly (without a subshell), providing array of arguments on Unix [A]

	readfile:       	Synchronously read a file. Argument is a file path.

	writefile:      	Synchronously truncate and write a file.

	appendfile:     	Synchronously append a file.

	udp:            	Send and receive packets to specified UDP socket, from random UDP port  

	udp-listen:     	Bind an UDP socket to specified host:port, receive packet

	open-async:     	Open file for read and write and use it like a socket. [A]

	open-fd:        	Use specified file descriptor like a socket. [A]

	threadedstdio:  	[A] Stdin/stdout, spawning a thread (threaded version).

	-               	Read input from console, print to console. Uses threaded implementation even on UNIX unless requested by `--async-stdio` CLI option.

	unix:           	Connect to UNIX socket. Argument is filesystem path. [A]

	unix-listen:    	Listen for connections on a specified UNIX socket [A]

	unix-dgram:     	Send packets to one path, receive from the other. [A]

	abstract:       	Connect to UNIX abstract-namespaced socket. Argument is some string used as address. [A]

	abstract-listen:	Listen for connections on a specified abstract UNIX socket [A]

	abstract-dgram: 	Send packets to one address, receive from the other. [A]

	mirror:         	Simply copy output to input. No arguments needed.

	literalreply:   	Reply with a specified string for each input packet.

	clogged:        	Do nothing. Don't read or write any bytes. Keep connections in "hung" state. [A]

	literal:        	Output a string, discard input.

	assert:         	Check the input.  [A]

	assert2:        	Check the input. [A]

	seqpacket:      	Connect to AF_UNIX SOCK_SEQPACKET socket. Argument is a filesystem path. [A]

	seqpacket-listen:	Listen for connections on a specified AF_UNIX SOCK_SEQPACKET socket [A]

	random:         	Generate random bytes when being read from, discard written bytes.

Full list of overlays:

	ws-upgrade:     	WebSocket upgrader / raw server. Specify your own protocol instead of usual TCP. [A]

	http-request:   	[A] Issue HTTP request, receive a 1xx or 2xx reply, then pass

	http-post-sse:  	[A] Accept HTTP/1 request. Then, if it is GET,

	ssl-connect:    	Overlay to add TLS encryption atop of existing connection [A]

	ssl-accept:     	Accept an TLS connection using arbitrary backing stream. [A]

	reuse-raw:      	Reuse subspecifier for serving multiple clients: unpredictable mode. [A]

	broadcast:      	Reuse this connection for serving multiple clients, sending replies to all clients.

	autoreconnect:  	Re-establish underlying connection on any error or EOF

	ws-c:           	Low-level WebSocket connector. Argument is a some another address. [A]

	msg2line:       	Line filter: Turns messages from packet stream into lines of byte stream. [A]

	line2msg:       	Line filter: turn lines from byte stream into messages as delimited by '\\n' or '\\0' [A]

	lengthprefixed: 	Turn stream of bytes to/from data packets with length-prefixed framing.  [A]

	foreachmsg:     	Execute something for each incoming message.

	log:            	Log each buffer as it pass though the underlying connector.

	jsonrpc:        	[A] Turns messages like `abc 1,2` into `{"jsonrpc":"2.0","id":412, "method":"abc", "params":[1,2]}`.

	timestamp:      	[A] Prepend timestamp to each incoming message.

	socks5-connect: 	SOCKS5 proxy client (raw) [A]

	socks5-bind:    	SOCKS5 proxy client (raw, bind command) [A]

	crypto:         	[A] Encrypts written messages and decrypts (and verifies) read messages with a static key, using ChaCha20-Poly1305 algorithm.

	prometheus:     	[A] Account connections, messages, bytes and other data and expose Prometheus metrics on a separate port.

	exit_on_specific_byte:	[A] Turn specific byte into a EOF, allowing user to escape interactive Websocat session

	waitfordata:    	Wait for some data to pending being written before starting connecting. [A]

```



Some notes

---



* IPv6 is supported, surround your IP in square brackets or use it as is, depending on context.

* Web socket usage is not obligatory, you can use any specs on both sides.

* Typically one line in binary stream correspond to one WebSocket text message. This is adjustable with options.



Limitations

---



* It only connects (or serves) HTTP/1. [RFC 8441](https://www.rfc-editor.org/rfc/rfc8441) or [RFC 9220](https://www.rfc-editor.org/rfc/rfc9220.html) are not currently supported.

* It is not convenient when text and binary WebSocket messages are mixed. This affects `mirror:` specifier, making it a bit different from ws://echo.websocket.org. There are `--binary-prefix`, `--text-prefix` and `--base64` options to handle mixture of binary and text.

* Current version of Websocat don't receive notification about closed sockets. This makes serving without `-E` or `-u` options or in backpressure scenarios prone to socket leak.

* Readline is not integrated. Users are advices to wrap websocat using [`rlwrap`](https://linux.die.net/man/1/rlwrap) tool for more convenient CLI.

* Build process of current version of Websocat is not properly automated and is fragile.

* Main version (v1) is based on obsolete dependency versions that trigger security warnings and may become tricky to build. There is [new version (v4)](https://github.com/vi/websocat/tree/websocat4), but is not yet considered stable and [has many missing features](https://github.com/vi/websocat/issues/276).



See also

---



* [wstunnel](https://github.com/erebe/wstunnel)

* [wscat](https://github.com/websockets/wscat)

* [websocketd](https://github.com/joewalnes/websocketd)

* [wsd](https://github.com/alexanderGugel/wsd)