Additional Resources:
- WebSocket RFC: https://www.rfc-editor.org/rfc/rfc6455.html
- cURL documentation: https://curl.se/docs/manpage.html
WebSockets provide a way to establish two-way, real-time communication between client and a server. Compared to traditional HTTP requests, WebSockets offer continuous data exchange without the need for repeated connections, which means through a single TCP/IP socket connection. This makes them ideal for applications like live chat, streaming platforms, and real-time games.
However, not all tools directly support WebSockets out of the box. This guide will show you how to leverage cURL and explore alternative options to establish and interact with WebSocket connections.
Using cURL
While cURL doesn't natively support WebSockets, you can mimic the handshake process by manually specifying websocket specific headers and flags.
# Indicates a persistent connection with upgrade to WebSocket protocol
Connection: keep-alive, upgrade
Upgrade: websocket
# Random base64 encoded key
Sec-WebSocket-Key: <your_websocket_key>
Sec-WebSocket-Version: 13
💡 For cUrl not to terminate its process when there’s no stdout you should use
--no-bufferor-Nflag (for short).
From cUrl docs:
In normal work situations, curl uses a standard buffered output stream that has the effect that it outputs the data in chunks, not necessarily exactly when the data arrives. Using this option disables that buffering.
The following command connects to
wss://ws.garantex.org/?stream=global&stream=btcrub&stream=ext_markets&stream=order&stream=trade&stream=member_balance&stream=exchanger
and subscribes to various scenarios, defined on the server.
Notice how it specifically uses http1.1, because http2 works in a different way.
curl \
--no-buffer \
-sSv \
--http1.1 \
--header "Connection: keep-alive, upgrade" \
--header "Upgrade: websocket" \
--header "Sec-WebSocket-Key: N509hQQwSFGfanhbxP3F6g==" \
--header "Sec-WebSocket-Version: 13" \
--url-query "stream=global" \
--url-query "stream=btcrub" \
--url-query "stream=ext_markets" \
--url-query "stream=order" \
--url-query "stream=trade" \
--url-query "stream=member_balance" \
--url-query "stream=exchanger" \
https://ws.garantex.org/
Note:
-s or —silent to suppress progress meter
-S or —show-error in addition to -s disables progress meter but still show error messages
-v or --verbose to show request and response headers
You may use just a single query sting --url-query "stream=global&stream=btcrub&stream=ext_markets&stream=order&stream=trade&stream=member_balance&stream=exchanger”
Beyond cURL: Alternative WebSocket Clients
There are not many (that i could find)
- cUrl kind of supports it, but i have not tested if you can communicate to server via stdin
- httpie sadly does not support websocket protocol (both cli and gui app)
- postman does support websockets, but it’s paid software now
- insomnia is pretty good (but personally i like httpie more) and does support websockets (free for personal use)
There are dedicated cli utilities to working with websockets:
wscat is nodejs based (so you will actually need to set up node environment)
wscat -c "wss://ws.garantex.org/?stream=global"
websocat native command-line tool, but i found it a bit overly complicated for my sort of task
websocat "wss://ws.garantex.org/?stream=global"
Others to explore
Browser (any modern browser)
In ECMAScript 6 (ES6) WebSocket API was added to javascript, so you may simply open devtools console and type in:
// creates connection
const ws = new WebSocket('wss://ws.garantex.org/?stream=global');
// returns current state of the connection
ws.readyState
// prints out response messages
ws.onmessage = function (e) { console.log(e.data) };
// communicate with the server
ws.send('Hello world!');
// self explanatory
ws.close();
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