Add echo example with public echo server

Author: kelunik

examples/aerys.php

@@ -7,12 +7,13 @@
 
 // Connects to the websocket endpoint in demo.php provided with Aerys (https://github.com/amphp/aerys).
 Amp\Loop::run(function () {
-    /** @var \Amp\Websocket\Connection $connection */
+    /** @var Websocket\Connection $connection */
     $connection = yield Websocket\connect('ws://localhost:1337/ws');
     yield $connection->send('Hello!');
 
     $i = 0;
 
+    /** @var Websocket\Message $message */
     while ($message = yield $connection->receive()) {
         $payload = yield $message->buffer();
 

examples/kaazing-echo-demo.php

@@ -0,0 +1,34 @@
+<?php
+
+require dirname(__DIR__) . '/vendor/autoload.php';
+
+use Amp\Delayed;
+use Amp\Websocket;
+
+Amp\Loop::run(function () {
+    /** @var Websocket\Connection $connection */
+    $connection = yield Websocket\connect('ws://demos.kaazing.com/echo');
+    yield $connection->send('Hello!');
+
+    $i = 0;
+
+    /** @var Websocket\Message $message */
+    while ($message = yield $connection->receive()) {
+        $payload = yield $message->buffer();
+
+        printf("Received: %s\n", $payload);
+
+        if ($payload === 'Goodbye!') {
+            $connection->close();
+            break;
+        }
+
+        yield new Delayed(1000);
+
+        if ($i < 3) {
+            yield $connection->send('Ping: ' . ++$i);
+        } else {
+            yield $connection->send('Goodbye!');
+        }
+    }
+});