Info about using 0.0.0.0, plus warning about using it. (#3519)

* Info about using 0.0.0.0, plus warning about using it.

* Moved information to WebServer. Incls listen.

* More warnings about n.n.n.n

core/language/en-GB/Help/listen.tid

@@ -28,3 +28,6 @@ All parameters are optional with safe defaults, and can be specified in any orde
 * ''tls-cert'' - pathname of TLS certificate file (relative to wiki folder)
 * ''tls-key'' - pathname of TLS key file (relative to wiki folder)
 * ''debug-level'' - optional debug level; set to "debug" to view request details (defaults to "none")
+
+For information on opening up your instance to the entire local network, and possible security concerns, see the WebServer tiddler at TiddlyWiki.com.
+

core/language/en-GB/Help/server.tid

@@ -27,12 +27,15 @@ For example:
 --server 8080 $:/core/save/all text/plain text/html MyUserName passw0rd
 ```
 
-The username and password can be specified as empty strings if you need to set the hostname or pathprefix and don't want to require a password:
+The username and password can be specified as empty strings if you need to set the hostname or pathprefix and don't want to require a password.
+
 
 ```
 --server 8080 $:/core/save/all text/plain text/html "" "" 192.168.0.245
 ```
 
+Using an address like this exposes your system to the local network. For information on opening up your instance to the entire local network, and possible security concerns, see the WebServer tiddler at TiddlyWiki.com.
+
 To run multiple TiddlyWiki servers at the same time you'll need to put each one on a different port. It can be useful to use an environment variable to pass the port number to the Node.js process. This example references an environment variable called "MY_PORT_NUMBER":
 
 ```

editions/tw5.com/tiddlers/webserver/WebServer Parameter_ host.tid

@@ -1,6 +1,6 @@
 caption: host
 created: 20180630180123321
-modified: 20180702153356797
+modified: 20181107183151913
 tags: [[WebServer Parameters]]
 title: WebServer Parameter: host
 type: text/vnd.tiddlywiki
@@ -10,3 +10,5 @@ The [[web server configuration parameter|WebServer Parameters]] ''host'' is the
 * ''127.0.0.1'' (default) - only listens for connections from browsers on the same computer 
 * ''0.0.0.0'' - listens for connections on all network interfaces, and thus from any browser on a reachable network
 * ''n.n.n.n'' - listens for connections on the network interface with the specified IP address
+
+''Note:'' Using ''0.0.0.0'' or ''n.n.n.n'' in a public environment (e.g. coffee shop, library, airport) is inadvisable as it ''will'' expose your system to possible intrusion.

editions/tw5.com/tiddlers/webserver/WebServer.tid

@@ -1,5 +1,5 @@
 created: 20180626150526207
-modified: 20181002103605866
+modified: 20181107173250253
 tags: ListenCommand ServerCommand Features
 title: WebServer
 type: text/vnd.tiddlywiki
@@ -29,6 +29,8 @@ tiddlywiki mywikifolder --listen
 
 Visit http://127.0.0.1:8080/ to access the wiki. Access is anonymous, so anyone can read or write to the wiki.
 
+This will typically be available only to users on the local machine. For information on how to open the instance to the local network see the Web Server [[host|WebServer Parameter: host]] parameter entry. 
+
 !! Authenticated Access
 
 Adding [[username|WebServer Parameter: username]] and [[password|WebServer Parameter: password]] parameters enforces basic authentication for both reading and writing: