Test a WebSocket using curl.

curl-websocket.sh

curl --include \
     --no-buffer \
     --header "Connection: Upgrade" \
     --header "Upgrade: websocket" \
     --header "Host: example.com:80" \
     --header "Origin: http://example.com:80" \
     --header "Sec-WebSocket-Key: SGVsbG8sIHdvcmxkIQ==" \
     --header "Sec-WebSocket-Version: 13" \
     http://example.com:80/

did anybody try same command using TLS? to "wss://echo.websocket.org"

Replacing "http://" with "https://" in the curl command seems to do the trick.

Curious whether anyone has gotten a clean termination after the first message, along the lines of websocat --one-message .... I tried using --max-time, but the curl return status ends up being nonzero.

I recommend adding --http1.1 to your curl command. The Connection and Upgrade headers are not valid in http/2 and curl will use http/2 if your server supports it.

I lost a few hours trying to figure out why these headers were disappearing when debugging my httpd web socket rewrite rules for the first time.

Thanks, it works!

curl --include \
   --header "Connection: Upgrade" \
   --header "Upgrade: websocket" \
   --header "Sec-WebSocket-Key: qwerty" \
   http://localhost:8000/

This worked for me. I didn't need all the header items

Anyone know if you can use this to send data (i.e. from stdin or a file) through the web socket? I tried -T -, but that doesn't seem to work.

curl --include \
    -H "Connection: Upgrade" \
    -H "Upgrade: websocket" \
    -H "Sec-WebSocket-Key: qwerty" \
    -H "Sec-WebSocket-Version: 13" \
    https://example.com -k

Hi,

@silvioprog @jageee

I am also using this command:

curl -i -N -H "Connection: Upgrade" -H "Upgrade: websocket" -H "Host: echo.websocket.org" -H "Origin: https://www.websocket.org" https://echo.websocket.org

but I am getting a 200 response instead of the 101.

Any ideas?

1. You need to use HTTP/1.1
2. You have specified too few headers

$ curl --http1.1 -i -N -H 'Sec-Websocket-Version: 13' -H 'Sec-Websocket-Key: QUo86XL2bHszCCpigvKqHg==' -H "Connection: Upgrade" -H "Upgrade: websocket" -H "Host: echo.websocket.org" -H "Origin: https://www.websocket.org" https://echo.websocket.org
HTTP/1.1 101 Switching Protocols
upgrade: websocket
connection: Upgrade
sec-websocket-accept: 8dlVwoWynsF/RauFo6HjkWl7dLk=
date: Thu, 25 Apr 2024 14:28:01 GMT
server: Fly/610c12e9 (2024-04-23)
via: 1.1 fly.io
fly-request-id: 01HWATFYXA0Y3STERG1SCHNQS2-ams

 Request served by 7811941c69e658

Thanks @vi that worked perfectly!

I recommend adding --http1.1 to your curl command. The Connection and Upgrade headers are not valid in http/2 and curl will use http/2 if your server supports it.

I lost a few hours trying to figure out why these headers were disappearing when debugging my httpd web socket rewrite rules for the first time.

You saved my life haha. I wasted so much time thinking my move to E2EE was the issue but stupid ActionCable and AWS Target Group using HTTP/2 was the issue! 🤦

Time to look into AnyCable or something else. Thank you!

I got status code 400 :"

I tried to connect to websocket server with simple setup using ws library:

const { WebSocketServer } = require('ws');

const wss = new WebSocketServer({ port: 8080 });

wss.on('connection', function connection(ws) {
  ws.on('error', console.error);

  ws.on('message', function message(data) {
    console.log('received: %s', data);
  });

  ws.send('something');
});

and I can't use curl to test it:

curl --include \
     --no-buffer \
     --header "Connection: Upgrade" \
     --header "Upgrade: websocket" \
     --header "Host: localhost:8080" \
     --header "Origin: http://localhost:8080" \
     --header "Sec-WebSocket-Key: SGVsbG8sIHdvcmxkIQ==" \
     --header "Sec-WebSocket-Version: 13" \
     http://localhost:8080/
HTTP/1.1 400 Bad Request
Connection: close
Content-Type: text/html
Content-Length: 43

Missing or invalid Sec-WebSocket-Key header

browser developer tools on the network tab have copy as curl value, however it seems still no luck:

curl 'ws://localhost:8080/' -H 'User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:138.0) Gecko/20100101 Firefox/138.0' -H 'Accept: */*' -H 'Accept-Language: en-US,en;q=0.7,id;q=0.3' -H 'Accept-Encoding: gzip, deflate, br, zstd' -H 'Sec-WebSocket-Version: 13' -H 'Origin: null' -H 'Sec-WebSocket-Extensions: permessage-deflate' -H 'Sec-WebSocket-Key: 3tMWYzcHwmObiLR3nWOgsg==' -H 'Connection: keep-alive, Upgrade' -H 'Sec-Fetch-Dest: empty' -H 'Sec-Fetch-Mode: websocket' -H 'Sec-Fetch-Site: cross-site' -H 'Pragma: no-cache' -H 'Cache-Control: no-cache' -H 'Upgrade: websocket'
curl: (22) Refused WebSockets upgrade: 400

okay, changing Sec-WebSocket-key with the one provided from browser works (not sure why):

curl --include \
     --no-buffer \
     --header "Connection: Upgrade" \
     --header "Upgrade: websocket" \
     --header "Host: localhost:8080" \
     --header "Origin: http://localhost:8080" \
     --header "Sec-WebSocket-Key: 3tMWYzcHwmObiLR3nWOgsg==" \
     --header "Sec-WebSocket-Version: 13" \
     http://localhost:8080/
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: YLxhg+bEzrZXCaOyyI5QkRBIdT4=

�       something

EDIT:
after reading the wikipedia, turned out it just a random 16-byte encoded with base64, on Linux, you can generate it with:

head -c 16 /dev/urandom | base64

This was very helpful. Thanks so much. In my case I just needed to confirm that the websocket server could be connected to and the connection would be upgraded, but I see how the headers and other settings can be changed as needed for any particular situation.

Just got to know about this so posting here to help others

WebSocket has been supported by curl as a non-experimental feature since version 8.11.0 (November 6 2024). With the upcoming release of version 8.16.0, we are taking it a step further.

With that release, you can use WebSocket in a pipe from the command line. Like this:

curl --no-progress-meter -T . -N wss://echo.websocket.org/
Request served by 4d896d95b55478dsadsa
Hello!
Hello!
you just echo what I send?
you just echo what I send?
...

This command line contacts the “echo” server run by websocket.org which just sends back what it receives from the client. The command line options are:

-T .: tells curl to upload the data from stdin, in non-blocking fashion.
-N: to avoid buffering of output data, so that even a single character received from the server is on stdout right away.
--no-progress-meter: to avoid curl cluttering stderr with information about how much was sent/received.