# Function to check server availability
check_server_availability() {
    local url=$1

    curl --connect-timeout 3 --silent ${url} 1>/dev/null
    if [ $? -ne 0 ]; then
        echo "VPN must be enabled to connect to ${url}"
        exit 1
    fi
}

# Function to check server accessibility with a POST request
check_server_accessibility() {
    local url=$1
    local payload='[{"id":0,"params":["latest",false],"method":"eth_getBlockByNumber","jsonrpc":"2.0"}]'

    http_code=$(curl -s -o /dev/null -w "%{http_code}" -X POST ${url} -H "Content-Type: application/json" -d "${payload}")
    if [ "$http_code" -ne 200 ]; then
        echo "VPN must be enabled to access ${url} (HTTP status code: ${http_code})"
        exit 1
    fi
}