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WebSocket

HTML5 與 WebSocket

WebSocket 協定於 2011 年標準化，目的是讓瀏覽器能和伺服器建立穩定的雙向連線。在此之前，瀏覽器僅支援 HTTP 請求，並不適合雙向通訊。

WebSocket 以訊息為單位，適合做推播通知，也常用於聊天、回合制遊戲等。它本質上還是 TCP 連線，因此穩定但延遲高，不適合 VoIP 或即時動作遊戲（這類請見 WebRTC）。

由於 WebSocket 簡單、兼容性高又比 TCP 連線容易用，很快開始被原生 APP 採用，拿來和伺服器溝通。

Godot 在原生與 HTML5 匯出皆支援 WebSocket。

在 Godot 中使用 WebSocket

Godot 以 WebSocketPeer 提供 WebSocket 支援，並且可與高階多人 API 搭配使用。更多細節請見 高階多人連線。

警告

匯出到 Android 時，請在匯出專案或一鍵部署前，於 Android 匯出設定啟用 INTERNET 權限，否則所有網路連線都會被 Android 阻擋。

基本用戶端範例

本範例將示範如何建立 WebSocket 連線、並與遠端伺服器收發資料。

extends Node

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

# Our WebSocketClient instance.
var socket = WebSocketPeer.new()

func _ready():
    # Initiate connection to the given URL.
    var err = socket.connect_to_url(websocket_url)
    if err != OK:
        print("Unable to connect")
        set_process(false)
    else:
        # Wait for the socket to connect.
        await get_tree().create_timer(2).timeout

        # Send data.
        socket.send_text("Test packet")

func _process(_delta):
    # Call this in _process or _physics_process. Data transfer and state updates
    # will only happen when calling this function.
    socket.poll()

    # get_ready_state() tells you what state the socket is in.
    var state = socket.get_ready_state()

    # WebSocketPeer.STATE_OPEN means the socket is connected and ready
    # to send and receive data.
    if state == WebSocketPeer.STATE_OPEN:
        while socket.get_available_packet_count():
            print("Got data from server: ", socket.get_packet().get_string_from_utf8())

    # WebSocketPeer.STATE_CLOSING means the socket is closing.
    # It is important to keep polling for a clean close.
    elif state == WebSocketPeer.STATE_CLOSING:
        pass

    # WebSocketPeer.STATE_CLOSED means the connection has fully closed.
    # It is now safe to stop polling.
    elif state == WebSocketPeer.STATE_CLOSED:
        # The code will be -1 if the disconnection was not properly notified by the remote peer.
        var code = socket.get_close_code()
        print("WebSocket closed with code: %d. Clean: %s" % [code, code != -1])
        set_process(false) # Stop processing.

這將印出類似：

Got data from server: Request served by 7811941c69e658
Got data from server: Test packet

基本伺服器範例

這個範例將示範如何建立一個 WebSocket 伺服器收聽連線，並進行資料交換。

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.client_connected.connect(_connected)
    _server.client_disconnected.connect(_disconnected)
    _server.client_close_request.connect(_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.data_received.connect(_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()

當有用戶端連線時，將印出類似：

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

進階聊天室範例

一個更進階的聊天範例 (其選擇性地使用中級多人連線抽象層) 以及一個高階多人連線範例，可在 godot 範例專案 中的 networking/websocket_chat 和 networking/websocket_multiplayer 下取得。