# WebSocket

## HTML5 and WebSocket

The WebSocket protocol was standardized in 2011 with the original goal of allowing browsers to create stable and bidirectional connections with a server.
Before that, browsers used to only support HTTPRequests, which is not well-suited for bidirectional communication.

The protocol is quite simple, message based, and a very powerful tool to send push notifications to browsers, and has been used to implement chats, turn-based games, etc. It still uses a TCP connection, which is good for reliability but not for latency, so not good for real-time applications like VoIP and fast-paced games (see `WebRTC ( doc_webrtc )` for those use cases).

Due to its simplicity, its wide compatibility, and being easier to use than a raw TCP connection, WebSocket soon started to spread outside the browsers, in native applications as a mean to communicate with network servers.

Pandemonium supports WebSocket in both native and HTML5 exports.

## Using WebSocket in Pandemonium

WebSocket is implemented in Pandemonium via three main classes `WebSocketClient` for more details.

Warning:


    When exporting to Android, make sure to enable the `INTERNET`
    permission in the Android export preset before exporting the project or
    using one-click deploy. Otherwise, network communication of any kind will be
    blocked by Android.

#### Minimal client example

This example will show you how to create a WebSocket connection to a remote server, and how to send and receive data.

```

extends Node

# The URL we will connect to
export var websocket_url = "wss://libwebsockets.org"

# Our WebSocketClient instance
var _client = WebSocketClient.new()

func _ready():
    # Connect base signals to get notified of connection open, close, and errors.
    _client.connect("connection_closed", self, "_closed")
    _client.connect("connection_error", self, "_closed")
    _client.connect("connection_established", self, "_connected")
    # This signal is emitted when not using the Multiplayer API every time
    # a full packet is received.
    # Alternatively, you could check get_peer(1).get_available_packets() in a loop.
    _client.connect("data_received", self, "_on_data")

    # Initiate connection to the given URL.
    var err = _client.connect_to_url(websocket_url, ["lws-mirror-protocol"])
    if err != OK:
        print("Unable to connect")
        set_process(false)

func _closed(was_clean = false):
    # was_clean will tell you if the disconnection was correctly notified
    # by the remote peer before closing the socket.
    print("Closed, clean: ", was_clean)
    set_process(false)

func _connected(proto = ""):
    # This is called on connection, "proto" will be the selected WebSocket
    # sub-protocol (which is optional)
    print("Connected with protocol: ", proto)
    # You MUST always use get_peer(1).put_packet to send data to server,
    # and not put_packet directly when not using the MultiplayerAPI.
    _client.get_peer(1).put_packet("Test packet".to_utf8())

func _on_data():
    # Print the received packet, you MUST always use get_peer(1).get_packet
    # to receive data from server, and not get_packet directly when not
    # using the MultiplayerAPI.
    print("Got data from server: ", _client.get_peer(1).get_packet().get_string_from_utf8())

func _process(delta):
    # Call this in _process or _physics_process. Data transfer, and signals
    # emission will only happen when calling this function.
    _client.poll()
```

This will print:

```

Connected with protocol:
Got data from server: Test packet
```

#### Minimal server example

This example will show you how to create a WebSocket server that listens for remote connections, and how to send and receive data.

```

extends Node

# The port we will listen to
const PORT = 9080
# Our WebSocketServer instance
var _server = WebSocketServer.new()

func _ready():
    # Connect base signals to get notified of new client connections,
    # disconnections, and disconnect requests.
    _server.connect("client_connected", self, "_connected")
    _server.connect("client_disconnected", self, "_disconnected")
    _server.connect("client_close_request", self, "_close_request")
    # This signal is emitted when not using the Multiplayer API every time a
    # full packet is received.
    # Alternatively, you could check get_peer(PEER_ID).get_available_packets()
    # in a loop for each connected peer.
    _server.connect("data_received", self, "_on_data")
    # Start listening on the given port.
    var err = _server.listen(PORT)
    if err != OK:
        print("Unable to start server")
        set_process(false)

func _connected(id, proto):
    # This is called when a new peer connects, "id" will be the assigned peer id,
    # "proto" will be the selected WebSocket sub-protocol (which is optional)
    print("Client %d connected with protocol: %s" % [id, proto])

func _close_request(id, code, reason):
    # This is called when a client notifies that it wishes to close the connection,
    # providing a reason string and close code.
    print("Client %d disconnecting with code: %d, reason: %s" % [id, code, reason])

func _disconnected(id, was_clean = false):
    # This is called when a client disconnects, "id" will be the one of the
    # disconnecting client, "was_clean" will tell you if the disconnection
    # was correctly notified by the remote peer before closing the socket.
    print("Client %d disconnected, clean: %s" % [id, str(was_clean)])

func _on_data(id):
    # Print the received packet, you MUST always use get_peer(id).get_packet to receive data,
    # and not get_packet directly when not using the MultiplayerAPI.
    var pkt = _server.get_peer(id).get_packet()
    print("Got data from client %d: %s ... echoing" % [id, pkt.get_string_from_utf8()])
    _server.get_peer(id).put_packet(pkt)

func _process(delta):
    # Call this in _process or _physics_process.
    # Data transfer, and signals emission will only happen when calling this function.
    _server.poll()
```

This will print (when a client connects) something similar to this:

```

Client 1348090059 connected with protocol: selected-protocol
Got data from client 1348090059: Test packet ... echoing
```

#### Advanced chat demo

A more advanced chat demo which optionally uses the multiplayer mid-level abstraction and a high level multiplayer demo are available in the `pandemonium demo projects ( https://github.com/Relintai/pandemonium_engine-demo-projects )` under `networking/websocket_chat` and `networking/websocket_multiplayer`.