websocat

Netcat, curl and socat for WebSockets.

Examples

Connect to public echo server

$ websocat ws://echo.websocket.org
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 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

See 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.
• 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.).
• Buildable by Rust starting from v1.34. Websocats up to version 1.5.0 are buildable by Rust 1.31. Websocat version 1.2.0 (or from a tag) should be buildable by 1.28.0. Websocat version 1.1.0 and earlier should be buildable with Rust v1.23.0. There is legacy non-async version buildable by even older Rust.

Installation

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

• If you're on Linux Debian or Ubuntu (or other dpkg-based), try downloading a pre-build deb package from GitHub releases and install from GUI or with command like gdebi websocat_..._.deb
• If you're on Fedora, you can install WebSocat from Copr: sudo dnf copr enable atim/websocat -y && sudo dnf install websocat
• If you're on FreeBSD, you may install WebSocat with the following command: pkg install websocat.
• If you're on Mac, you can do brew install websocat.
• Download a pre-build executable and install it to PATH.
• Install the Rust toolchain 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.

--help=long output

websocat 1.7.0
Vitaly "_Vi" Shukela <[email protected]>
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] <addr1> <addr2>  (advanced mode)

FLAGS:
        --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.
        --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
        --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 [].
        --just-generate-key                     [A] Just a Sec-WebSocket-Key value without running main Websocat
        --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)
        --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.
    -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.
    -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)
        --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 <auto_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 <autoreconnect_delay_millis>
            [A] Delay before reconnect attempt for `autoreconnect:` overlay. [default: 20]

        --queue-len <broadcast_queue_len>
            [A] Number of pending queued messages for broadcast reuser [default: 16]

    -B, --buffer-size <buffer_size>                                  Maximum message size, in bytes [default: 65536]
    -H, --header <custom_headers>...
            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 <custom_reply_headers>...
            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 <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 <headers_to_env>...
            Forward specified incoming request header to H_* environment variable for `exec:`-like specifiers.

    -h, --help <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.
        --just-generate-accept <just_generate_accept>
            [A] Just a Sec-WebSocket-Accept value based on supplied Sec-WebSocket-Key value without running main
            Websocat
        --max-messages <max_messages>
            Maximum number of messages to copy in one direction.

        --max-messages-rev <max_messages_rev>
            Maximum number of messages to copy in the other direction.

        --conncap <max_parallel_conns>
            Maximum number of simultaneous connections for listening mode

        --origin <origin>                                            Add Origin HTTP header to websocket client request
        --pkcs12-der <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 <pkcs12_passwd>
            Password for --pkcs12-der pkcs12 archive. Required on Mac.

        --request-header <request_headers>...
            [A] Specify HTTP request headers for `http-request:` specifier.

    -X, --request-method <request_method>                            [A] Method to use for `http-request:` specifier
        --request-uri <request_uri>                                  [A] URI to use for `http-request:` specifier
        --restrict-uri <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_static_files>...
            Serve a named static file for non-websocket connections.
            Argument syntax: <URI>:<Content-Type>:<file-path>
            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 <socks5_bind_script>
            [A] Execute specified script in `socks5-bind:` mode when remote port number becomes known.

        --socks5-destination <socks_destination>
            [A] Examples: 1.2.3.4:5678  2600:::80  hostname:5678

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

        --udp-multicast <udp_join_multicast_addr>...
            [A] Issue IP[V6]_ADD_MEMBERSHIP for specified multicast address. Can be specified multiple times.

        --udp-multicast-iface-v4 <udp_join_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 <udp_join_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 <udp_ttl>                                          [A] Set IP_TTL, also IP_MULTICAST_TTL if applicable
        --protocol <websocket_protocol>
            Specify this Sec-WebSocket-Protocol: header when connecting

        --server-protocol <websocket_reply_protocol>
            Force this Sec-WebSocket-Protocol: header when accepting a connection

        --websocket-version <websocket_version>                      Override the Sec-WebSocket-Version value
        --binary-prefix <ws_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 <ws_c_uri>
            [A] URI to use for ws-c: overlay [default: ws://0.0.0.0/]

        --ping-interval <ws_ping_interval>                           Send WebSocket pings each this number of seconds
        --ping-timeout <ws_ping_timeout>
            Drop WebSocket connection if Pong message not received for this number of seconds

        --text-prefix <ws_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:
    <addr1>    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.
    <addr2>    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://echo.websocket.org/
    
  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 intented 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]
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]
	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]}`.
	socks5-connect: 	SOCKS5 proxy client (raw) [A]
	socks5-bind:    	SOCKS5 proxy client (raw, bind command) [A]

Pre-built binaries for Linux (usual and musl), Windows, OS X and Android are available on the releases page.

Building from source code

1. Install the Rust toolchain
2. cargo build --release --features=ssl.
3. Find the executable somewhere under target/, e.g. in target/release/websocat.

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.

Reference

There is a work-in-progress reference document that contains more options and examples.

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 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 tool for more convenient CLI.
• Build process of current version of Websocat is not properly automated and is fragile.

See also

• wstunnel
• wscat
• websocketd
• wsd