A simple bash script for checking if a WebSocket endpoint is alive.

websocket_handshake_probe.sh

#!/bin/bash

self=`basename "$0"`

if (($# == 0)); then
    cat <<EOF
    Usage: $self url
    Example: $self http://localhost:3000/echo

    Check if a URL is returning a valid WebSocket handshake response.
    This is useful for healthcheck and liveness probes.

    Note: Use an http/https for the URL scheme instead of ws/wss.
EOF
    exit 1
fi

url=$1

code=`curl \
  --silent \
  --header "Upgrade: websocket" \
  --header "Connection: upgrade" \
  --header "Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==" \
  --header "Sec-WebSocket-Version: 13" \
  --max-time 1 \
  --write "%{http_code}" \
  "$url"`

if [ "$code" = "101" ]; then
  echo "it's alive"
  exit 0
else
  echo "it's dead"
  exit 1
fi