modify unused_addr method; update websockt guide section

guide/src/SUMMARY.md

@@ -9,8 +9,8 @@
 - [URL Dispatch](./qs_5.md)
 - [Request & Response](./qs_7.md)
 - [Testing](./qs_8.md)
-- [WebSockets](./qs_9.md)
 - [Middlewares](./qs_10.md)
 - [Static file handling](./qs_12.md)
+- [WebSockets](./qs_9.md)
 - [HTTP/2](./qs_13.md)
 - [Database integration](./qs_14.md)

guide/src/qs_9.md

@@ -1,4 +1,49 @@
 # WebSockets
 
-[WIP]
+Actix supports WebSockets out-of-the-box. It is possible to convert request's `Payload`
+to a stream of [*ws::Message*](../actix_web/ws/enum.Message.html) with 
+a [*ws::WsStream*](../actix_web/ws/struct.WsStream.html) and then use stream
+combinators to handle actual messages. But it is simplier to handle websocket communication
+with http actor.
 
+```rust
+extern crate actix;
+extern crate actix_web;
+
+use actix::*;
+use actix_web::*;
+
+/// Define http actor
+struct Ws;
+
+impl Actor for Ws {
+    type Context = HttpContext<Self>;
+}
+
+/// Define Handler for ws::Message message
+# impl StreamHandler<ws::Message> for WsRoute {}
+impl Handler<ws::Message> for WsRoute {
+    fn handle(&mut self, msg: ws::Message, ctx: &mut HttpContext<Self>) -> Response<Self, ws::Message>
+    {
+        match msg {
+            ws::Message::Ping(msg) => ws::WsWriter::pong(ctx, &msg),
+            ws::Message::Text(text) => ws::WsWriter::text(ctx, &text),
+            ws::Message::Binary(bin) => ws::WsWriter::binary(ctx, bin),
+            _ => (),
+        }
+        Self::empty()
+    }
+}
+
+fn main() {
+    Application::new()
+      .resource("/ws/", |r| r.f(|req| ws::start(req, WS))  // <- register websocket route
+      .finish();
+}
+```
+
+Simple websocket echo server example is available in 
+[examples directory](https://github.com/actix/actix-web/blob/master/examples/websocket.rs).
+
+Example chat server with ability to chat over websocket connection or tcp connection
+is available in [websocket-chat directory](https://github.com/actix/actix-web/tree/master/examples/websocket-chat/)