doc / bring back detailed APIs

docs/usage.md

@@ -1,8 +1,8 @@
-## Examples
+# Examples
 
 The [*ws*](https://github.com/machinezone/IXWebSocket/tree/master/ws) folder countains many interactive programs for chat, [file transfers](https://github.com/machinezone/IXWebSocket/blob/master/ws/ws_send.cpp), [curl like](https://github.com/machinezone/IXWebSocket/blob/master/ws/ws_http_client.cpp) http clients, demonstrating client and server usage.
 
-### Windows note
+## Windows note
 
 To use the network system on Windows, you need to initialize it once with *WSAStartup()* and clean it up with *WSACleanup()*. We have helpers for that which you can use, see below. This init would typically take place in your main function.
 
@@ -20,7 +20,7 @@ int main()
 }
 ```
 
-### WebSocket client API
+## WebSocket client API
 
 ```
 #include <ixwebsocket/IXWebSocket.h>
@@ -65,7 +65,129 @@ webSocket.sendBinary("some serialized binary data");
 webSocket.stop()
 ```
 
-### WebSocket server API
+### Sending messages
+
+`websocket.send("foo")` will send a message.
+
+If the connection was closed and sending failed, the return value will be set to false.
+
+### ReadyState
+
+`getReadyState()` returns the state of the connection. There are 4 possible states.
+
+1. ReadyState::Connecting - The connection is not yet open.
+2. ReadyState::Open       - The connection is open and ready to communicate.
+3. ReadyState::Closing    - The connection is in the process of closing.
+4. ReadyState::Closed     - The connection is closed or could not be opened.
+
+### Open and Close notifications
+
+The onMessage event will be fired when the connection is opened or closed. This is similar to the [Javascript browser API](https://developer.mozilla.org/en-US/docs/Web/API/WebSocket), which has `open` and `close` events notification that can be registered with the browser `addEventListener`.
+
+```
+webSocket.setOnMessageCallback([](const ix::WebSocketMessagePtr& msg)
+    {
+        if (msg->type == ix::WebSocketMessageType::Open)
+        {
+            std::cout << "send greetings" << std::endl;
+
+            // Headers can be inspected (pairs of string/string)
+            std::cout << "Handshake Headers:" << std::endl;
+            for (auto it : msg->headers)
+            {
+                std::cout << it.first << ": " << it.second << std::endl;
+            }
+        }
+        else if (msg->type == ix::WebSocketMessageType::Close)
+        {
+            std::cout << "disconnected" << std::endl;
+
+            // The server can send an explicit code and reason for closing.
+            // This data can be accessed through the closeInfo object.
+            std::cout << msg->closeInfo.code << std::endl;
+            std::cout << msg->closeInfo.reason << std::endl;
+        }
+    }
+);
+```
+
+### Error notification
+
+A message will be fired when there is an error with the connection. The message type will be `ix::WebSocketMessageType::Error`. Multiple fields will be available on the event to describe the error.
+
+```
+webSocket.setOnMessageCallback([](const ix::WebSocketMessagePtr& msg)
+    {
+        if (msg->type == ix::WebSocketMessageType::Error)
+        {
+            std::stringstream ss;
+            ss << "Error: "         << msg->errorInfo.reason      << std::endl;
+            ss << "#retries: "      << msg->eventInfo.retries     << std::endl;
+            ss << "Wait time(ms): " << msg->eventInfo.wait_time   << std::endl;
+            ss << "HTTP Status: "   << msg->eventInfo.http_status << std::endl;
+            std::cout << ss.str() << std::endl;
+        }
+    }
+);
+```
+
+### start, stop
+
+1. `websocket.start()` connect to the remote server and starts the message receiving background thread.
+2. `websocket.stop()` disconnect from the remote server and closes the background thread.
+
+### Configuring the remote url
+
+The url can be set and queried after a websocket object has been created. You will have to call `stop` and `start` if you want to disconnect and connect to that new url.
+
+```
+std::string url("wss://example.com");
+websocket.configure(url);
+```
+
+### Ping/Pong support
+
+Ping/pong messages are used to implement keep-alive. 2 message types exists to identify ping and pong messages. Note that when a ping message is received, a pong is instantly send back as requested by the WebSocket spec.
+
+```
+webSocket.setOnMessageCallback([](const ix::WebSocketMessagePtr& msg)
+    {
+        if (msg->type == ix::WebSocketMessageType::Ping ||
+            msg->type == ix::WebSocketMessageType::Pong)
+        {
+            std::cout << "pong data: " << msg->str << std::endl;
+        }
+    }
+);
+```
+
+A ping message can be sent to the server, with an optional data string.
+
+```
+websocket.ping("ping data, optional (empty string is ok): limited to 125 bytes long");
+```
+
+### Heartbeat.
+
+You can configure an optional heart beat / keep-alive, sent every 45 seconds
+when there is no any traffic to make sure that load balancers do not kill an
+idle connection.
+
+```
+webSocket.setHeartBeatPeriod(45);
+```
+
+### Supply extra HTTP headers.
+
+You can set extra HTTP headers to be sent during the WebSocket handshake.
+
+```
+WebSocketHttpHeaders headers;
+headers["foo"] = "bar";
+webSocket.setExtraHeaders(headers);
+```
+
+## WebSocket server API
 
 ```
 #include <ixwebsocket/IXWebSocketServer.h>
@@ -130,7 +252,7 @@ server.wait();
 
 ```
 
-### HTTP client API
+## HTTP client API
 
 ```
 #include <ixwebsocket/IXHttpClient.h>
@@ -213,7 +335,7 @@ bool ok = httpClient.performRequest(args, [](const HttpResponsePtr& response)
 // ok will be false if your httpClient is not async
 ```
 
-### HTTP server API
+## HTTP server API
 
 ```
 #include <ixwebsocket/IXHttpServer.h>