diff --git a/rak/error_number.h b/rak/error_number.h
index d808dc39..224c3b0b 100644
--- a/rak/error_number.h
+++ b/rak/error_number.h
@@ -44,6 +44,12 @@ namespace rak {
 
 class error_number {
 public:
+  static const int e_again       = EAGAIN;
+  static const int e_intr        = EINTR;
+  static const int e_deadlk      = EDEADLK;
+  static const int e_connreset   = ECONNRESET;
+  static const int e_connaborted = ECONNABORTED;
+
   error_number() : m_errno(0) {}
   error_number(int e) : m_errno(e) {}
 
@@ -52,10 +58,10 @@ public:
   int                 value() const                { return m_errno; }
   const char*         c_str() const                { return strerror(m_errno); }
 
-  bool                is_blocked_momentary() const { return m_errno == EAGAIN || m_errno == EINTR; }
-  bool                is_blocked_prolonged() const { return m_errno == EDEADLK; }
+  bool                is_blocked_momentary() const { return m_errno == e_again || m_errno == e_intr; }
+  bool                is_blocked_prolonged() const { return m_errno == e_deadlk; }
 
-  bool                is_closed() const            { return m_errno == ECONNRESET || m_errno == ECONNABORTED; }
+  bool                is_closed() const            { return m_errno == e_connreset || m_errno == e_connaborted; }
 
   static error_number current()                    { return errno; }
   static void         clear_global()               { errno = 0; }
diff --git a/rak/ranges.h b/rak/ranges.h
index a2440ceb..cd563962 100644
--- a/rak/ranges.h
+++ b/rak/ranges.h
@@ -67,13 +67,14 @@ public:
 //   void                erase(value_type r);
 
   // Find the first ranges that has an end greater than index.
-  inline iterator     find(Type index);
+  iterator            find(Type index);
+  const_iterator      find(Type index) const;
 
   // Use find with no closest match.
-  inline bool         has(Type index);
+  bool                has(Type index) const;
 
 private:
-  inline void         unify(iterator itr);
+  void                unify(iterator itr);
 };
 
 template <typename Type>
@@ -109,10 +110,16 @@ ranges<Type>::find(Type index) {
   return std::find_if(begin(), end(), rak::less(index, rak::mem_ptr_ref(&value_type::second)));
 }
 
+template <typename Type>
+inline typename ranges<Type>::const_iterator
+ranges<Type>::find(Type index) const {
+  return std::find_if(begin(), end(), rak::less(index, rak::mem_ptr_ref(&value_type::second)));
+}
+
 // Use find with no closest match.
 template <typename Type>
 inline bool
-ranges<Type>::has(Type index) {
+ranges<Type>::has(Type index) const {
   const_iterator itr = find(index);
 
   return itr != end() && index >= itr->first;