nathelper: fix force_socket documentation

src/modules/nathelper/README

@@ -249,14 +249,15 @@ Chapter 1. Admin Guide
 
 4.1. force_socket (string)
 
-   Socket to be used when sending NAT pings for UDP communication. If no
-   one specified, the OS will choose a socket.
+   Socket to be used when sending NAT pings for UDP communication.
+   It uses the first socket it finds based on the IP address. If
+   no one specified, the OS will choose a socket.
 
    Default value is “NULL”.
 
    Example 1.1. Set force_socket parameter
 ...
-modparam("nathelper", "force_socket", "localhost:33333")
+modparam("nathelper", "force_socket", "127.0.0.1")
 ...
 
 4.2. natping_interval (integer)

src/modules/nathelper/doc/nathelper_admin.xml

@@ -128,7 +128,8 @@
 		<title><varname>force_socket</varname> (string)</title>
 		<para>
 		Socket to be used when sending NAT pings for UDP communication.
-		If no one specified, the OS will choose a socket.
+		It uses the first socket it finds based on the IP address. If
+		no one specified, the OS will choose a socket.
 		</para>
 		<para>
 		<emphasis>
@@ -139,7 +140,7 @@
 		<title>Set <varname>force_socket</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
-modparam("nathelper", "force_socket", "localhost:33333")
+modparam("nathelper", "force_socket", "127.0.0.1")
 ...
 </programlisting>
 		</example>