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-syscrate, try without--features=ssl; - Build Websocat from source code (see below), then move
target/release/websocatsomewhere to the PATH.
--help=long output
websocat 1.7.0
Vitaly "_Vi" Shukela <vi0oss@gmail.com>
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
- Install the Rust toolchain
cargo build --release --features=ssl.- Find the executable somewhere under
target/, e.g. intarget/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-prefixand--base64options to handle mixture of binary and text. - Current version of Websocat don't receive notification about closed sockets. This makes serving without
-Eor-uoptions or in backpressure scenarios prone to socket leak. - Readline is not integrated. Users are advices to wrap websocat using
rlwraptool for more convenient CLI. - Build process of current version of Websocat is not properly automated and is fragile.