diff --git a/cf_ufw.sh b/cf_ufw.sh
index a982879..2ebac4b 100644
--- a/cf_ufw.sh
+++ b/cf_ufw.sh
@@ -1,4 +1,4 @@
-#!/usr/bin/env sh
+#!/bin/sh
 
 # This script updates the UFW rules to permit only HTTP and HTTPS traffic originating from Cloudflare IP addresses.
 # For further information and documentation, visit:
@@ -7,43 +7,64 @@
 set -eu
 
 # Define variables
-TMP_FILE=$(mktemp)
-IPv4_URL="https://www.cloudflare.com/ips-v4"
-IPv6_URL="https://www.cloudflare.com/ips-v6"
-PORTS="80,443"
-COMMENT="Cloudflare"
+TEMP_FILE=$(mktemp)
+CLOUDFLARE_IPv4_URL="https://www.cloudflare.com/ips-v4"
+CLOUDFLARE_IPv6_URL="https://www.cloudflare.com/ips-v6"
+ALLOWED_PORTS="80,443"
+RULE_COMMENT="Cloudflare"
+
+# Check if the required tools are installed
+check_dependencies() {
+  if ! command -v ufw > /dev/null; then
+    echo "UFW is not installed. Aborting."
+    exit 1
+  fi
+
+  if ! command -v curl > /dev/null; then
+    echo "curl is not installed. Aborting."
+    exit 1
+  fi
+}
+
+# Check if the user has sufficient permissions
+check_permissions() {
+  if [ "$(id -u)" -ne 0 ]; then
+    echo "This script must be run as root. Aborting."
+    exit 1
+  fi
+}
 
 # Fetch the latest Cloudflare IP ranges and update UFW rules accordingly
 fetch_and_update_ranges() {
   # Retrieve the latest IPv4 and IPv6 IP ranges from Cloudflare.
-  curl -s "$IPv4_URL" -o "$TMP_FILE"
-  echo "" >> "$TMP_FILE"
-  curl -s "$IPv6_URL" >> "$TMP_FILE"
+  if ! curl -s --retry 3 --retry-delay 5 "$CLOUDFLARE_IPv4_URL" -o "$TEMP_FILE"; then
+    echo "Failed to fetch IPv4 addresses. Aborting."
+    exit 1
+  fi
+
+  echo "" >> "$TEMP_FILE"
+
+  if ! curl -s --retry 3 --retry-delay 5 "$CLOUDFLARE_IPv6_URL" >> "$TEMP_FILE"; then
+    echo "Failed to fetch IPv6 addresses. Aborting."
+    exit 1
+  fi
 
   # Update UFW rules to allow traffic only on ports 80 (TCP) and 443 (TCP) from the fetched IP ranges.
   # If a rule for a specific subnet already exists, UFW will not create a duplicate rule.
   while IFS= read -r ip; do
-    ufw allow from "$ip" to any port "$PORTS" proto tcp comment "$COMMENT"
-  done < "$TMP_FILE"
+    ufw allow from "$ip" to any port "$ALLOWED_PORTS" proto tcp comment "$RULE_COMMENT"
+  done < "$TEMP_FILE"
 
   # Remove the temporary file containing the IP ranges.
-  rm "$TMP_FILE"
+  rm "$TEMP_FILE"
 }
 
-# Check if UFW is installed
-if ! command -v ufw > /dev/null; then
-  echo "UFW is not installed. Aborting."
-  exit 1
-fi
-
-# Check if the user has sufficient permissions
-if [ "$(id -u)" -ne 0 ]; then
-  echo "This script must be run as root. Aborting."
-  exit 1
-fi
-
-# Call the fetch_and_update_ranges function to update the UFW rules
-fetch_and_update_ranges
+# Main function to run the script
+main() {
+  check_dependencies
+  check_permissions
+  fetch_and_update_ranges
+  ufw reload
+}
 
-# Reload UFW to apply the updated rules
-ufw reload
+main