diff --git a/start.sh b/start.sh
index 03e725c..99438bb 100755
--- a/start.sh
+++ b/start.sh
@@ -69,10 +69,24 @@ if [[ ! -f "$ENV_FILE" ]]; then
 fi
 
 # Safe reader for existing values (does not fail under set -e -o pipefail)
+# Returns only the value part after the first "=", empty string if key missing or value is empty.
 ini_val() {
   local key="$1"
   local val
-  val=$(awk -F'=' -v k="$key" 'BEGIN{found=0} $1==k{print substr($0, index($0,$2)); found=1} END{ if(!found){} }' "$ENV_FILE" 2>/dev/null || true)
+  val=$(awk -F'=' -v k="$key" '
+    $1 == k {
+      if (NF == 1) {
+        # Key present but no "=", treat as empty value
+        print ""
+      } else {
+        # Reconstruct everything after the first "="
+        $1 = ""
+        sub(/^=/, "", $0)
+        print $0
+      }
+      exit
+    }
+  ' "$ENV_FILE" 2>/dev/null || true)
   echo -n "$val"
 }
 
@@ -104,6 +118,16 @@ sanitize_assignment() {
   echo "$value"
 }
 
+is_valid_port() {
+  local p="$1"
+  [[ "$p" =~ ^[0-9]+$ ]] && (( p > 0 && p <= 65535 ))
+}
+
+is_positive_int() {
+  local n="$1"
+  [[ "$n" =~ ^[0-9]+$ ]] && (( n > 0 ))
+}
+
 # Helper to prompt only if missing in .env
 ask_or_keep() {
   local key="$1"; shift
@@ -136,6 +160,88 @@ ask_or_keep() {
   eval "$key=\"$val\""
 }
 
+# Helper specifically for port values: validates and reprompts until a correct port is provided.
+ask_port_or_keep() {
+  local key="$1"; shift
+  local prompt="$1"; shift
+  local def="${1:-}"
+
+  local cur
+  cur=$(ini_val "$key")
+  cur=$(sanitize_assignment "$key" "$cur")
+
+  if is_valid_port "$cur"; then
+    echo "$key is set in .env; keeping existing value ($cur)"
+    eval "$key=\"$cur\""
+    return
+  elif [[ -n "$cur" ]]; then
+    echo "Existing value for $key in .env is invalid ('$cur'); you will be asked to enter a valid port."
+  fi
+
+  local hint
+  hint=$(sanitize_assignment "$key" "$def")
+  if ! is_valid_port "$hint"; then
+    hint=""
+  fi
+
+  while true; do
+    local val
+    if [[ -n "$hint" ]]; then
+      read -rp "$prompt (1-65535) [${hint}]: " val || true
+      val=${val:-$hint}
+    else
+      read -rp "$prompt (1-65535): " val || true
+    fi
+    val=$(sanitize_assignment "$key" "$val")
+    if is_valid_port "$val"; then
+      eval "$key=\"$val\""
+      break
+    fi
+    echo "Invalid port '$val'. Please enter a number between 1 and 65535."
+  done
+}
+
+# Helper for positive integer values (e.g. intervals)
+ask_positive_int_or_keep() {
+  local key="$1"; shift
+  local prompt="$1"; shift
+  local def="${1:-}"
+
+  local cur
+  cur=$(ini_val "$key")
+  cur=$(sanitize_assignment "$key" "$cur")
+
+  if is_positive_int "$cur"; then
+    echo "$key is set in .env; keeping existing value ($cur)"
+    eval "$key=\"$cur\""
+    return
+  elif [[ -n "$cur" ]]; then
+    echo "Existing value for $key in .env is invalid ('$cur'); you will be asked to enter a valid integer."
+  fi
+
+  local hint
+  hint=$(sanitize_assignment "$key" "$def")
+  if ! is_positive_int "$hint"; then
+    hint="60"
+  fi
+
+  while true; do
+    local val
+    if [[ -n "$hint" ]]; then
+      read -rp "$prompt (integer) [${hint}]: " val || true
+      val=${val:-$hint}
+    else
+      read -rp "$prompt (integer): " val || true
+    fi
+    val=$(sanitize_assignment "$key" "$val")
+    if is_positive_int "$val"; then
+      eval "$key=\"$val\""
+      break
+    fi
+    echo "Invalid value '$val'. Please enter a positive integer."
+  done
+}
+
 if [[ "$NODE_PRIVACY" == "private" ]]; then
   # For private nodes, PUBLIC_HOST optional; only ask if missing
   ask_or_keep PUBLIC_HOST "Public host URL (leave empty for private)" ""
@@ -143,10 +249,10 @@ else
   ask_or_keep PUBLIC_HOST "Public host URL (e.g., https://node.example.com)" "$(ini_val PUBLIC_HOST)"
 fi
 
-ask_or_keep SANIC_PORT "Internal app port (SANIC_PORT)" "$(ini_val SANIC_PORT)"
-ask_or_keep BACKEND_HTTP_PORT "Published backend port on host (BACKEND_HTTP_PORT)" "$(ini_val BACKEND_HTTP_PORT)"
+ask_port_or_keep SANIC_PORT "Internal app port (SANIC_PORT)" "$(ini_val SANIC_PORT)"
+ask_port_or_keep BACKEND_HTTP_PORT "Published backend port on host (BACKEND_HTTP_PORT)" "$(ini_val BACKEND_HTTP_PORT)"
 ask_or_keep BOOTSTRAP_SEEDS "Bootstrap seeds (comma-separated URLs)" "" "https://my-bootstrap-1.example.com,https://my-bootstrap-2.example.com"
-ask_or_keep HANDSHAKE_INTERVAL_SEC "Handshake interval seconds" "$(ini_val HANDSHAKE_INTERVAL_SEC)"
+ask_positive_int_or_keep HANDSHAKE_INTERVAL_SEC "Handshake interval seconds" "$(ini_val HANDSHAKE_INTERVAL_SEC)"
 ask_or_keep TELEGRAM_API_KEY "Telegram uploader bot token (TELEGRAM_API_KEY)" "" "YOUR_UPLOADER_BOT_TOKEN"
 ask_or_keep CLIENT_TELEGRAM_API_KEY "Telegram client bot token (CLIENT_TELEGRAM_API_KEY)" "" "YOUR_CLIENT_BOT_TOKEN"