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WebSockets

在定义 WebSockets 时，通常会声明一个类型为 WebSocket 的参数，通过它你可以从客户端读取数据并向其发送数据。

它由 Starlette 直接提供，但你也可以从 fastapi 导入它：

from fastapi import WebSocket

Tip

当你想要定义一个既兼容 HTTP 又兼容 WebSockets 的依赖项时，你可以定义一个接受 HTTPConnection 而不是 Request 或 WebSocket 的参数。

fastapi.WebSocket 

WebSocket(scope, receive, send)

Bases: HTTPConnection

PARAMETER DESCRIPTION
scope

TYPE: Scope

receive

TYPE: Receive

send

TYPE: Send

Source code in starlette/websockets.py 
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def __init__(self, scope: Scope, receive: Receive, send: Send) -> None:
    super().__init__(scope)
    assert scope["type"] == "websocket"
    self._receive = receive
    self._send = send
    self.client_state = WebSocketState.CONNECTING
    self.application_state = WebSocketState.CONNECTING

scope instance-attribute 

scope = scope

app property 

app

url property 

url

base_url property 

base_url

headers property 

headers

query_params property 

query_params

path_params property 

path_params

cookies property 

cookies

client property 

client

state property 

state

client_state instance-attribute 

client_state = CONNECTING

application_state instance-attribute 

application_state = CONNECTING

url_for 

url_for(name, /, **path_params)
PARAMETER DESCRIPTION
name

TYPE: str

**path_params

TYPE: Any DEFAULT: {}

Source code in starlette/requests.py 
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def url_for(self, name: str, /, **path_params: typing.Any) -> URL:
    router: Router = self.scope["router"]
    url_path = router.url_path_for(name, **path_params)
    return url_path.make_absolute_url(base_url=self.base_url)

receive async 

receive()

Receive ASGI websocket messages, ensuring valid state transitions.

Source code in starlette/websockets.py 
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async def receive(self) -> Message:
    """
    Receive ASGI websocket messages, ensuring valid state transitions.
    """
    if self.client_state == WebSocketState.CONNECTING:
        message = await self._receive()
        message_type = message["type"]
        if message_type != "websocket.connect":
            raise RuntimeError(f'Expected ASGI message "websocket.connect", but got {message_type!r}')
        self.client_state = WebSocketState.CONNECTED
        return message
    elif self.client_state == WebSocketState.CONNECTED:
        message = await self._receive()
        message_type = message["type"]
        if message_type not in {"websocket.receive", "websocket.disconnect"}:
            raise RuntimeError(
                f'Expected ASGI message "websocket.receive" or "websocket.disconnect", but got {message_type!r}'
            )
        if message_type == "websocket.disconnect":
            self.client_state = WebSocketState.DISCONNECTED
        return message
    else:
        raise RuntimeError('Cannot call "receive" once a disconnect message has been received.')

send async 

send(message)

Send ASGI websocket messages, ensuring valid state transitions.

PARAMETER DESCRIPTION
message

TYPE: Message

Source code in starlette/websockets.py 
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async def send(self, message: Message) -> None:
    """
    Send ASGI websocket messages, ensuring valid state transitions.
    """
    if self.application_state == WebSocketState.CONNECTING:
        message_type = message["type"]
        if message_type not in {"websocket.accept", "websocket.close", "websocket.http.response.start"}:
            raise RuntimeError(
                'Expected ASGI message "websocket.accept", "websocket.close" or "websocket.http.response.start", '
                f"but got {message_type!r}"
            )
        if message_type == "websocket.close":
            self.application_state = WebSocketState.DISCONNECTED
        elif message_type == "websocket.http.response.start":
            self.application_state = WebSocketState.RESPONSE
        else:
            self.application_state = WebSocketState.CONNECTED
        await self._send(message)
    elif self.application_state == WebSocketState.CONNECTED:
        message_type = message["type"]
        if message_type not in {"websocket.send", "websocket.close"}:
            raise RuntimeError(
                f'Expected ASGI message "websocket.send" or "websocket.close", but got {message_type!r}'
            )
        if message_type == "websocket.close":
            self.application_state = WebSocketState.DISCONNECTED
        try:
            await self._send(message)
        except OSError:
            self.application_state = WebSocketState.DISCONNECTED
            raise WebSocketDisconnect(code=1006)
    elif self.application_state == WebSocketState.RESPONSE:
        message_type = message["type"]
        if message_type != "websocket.http.response.body":
            raise RuntimeError(f'Expected ASGI message "websocket.http.response.body", but got {message_type!r}')
        if not message.get("more_body", False):
            self.application_state = WebSocketState.DISCONNECTED
        await self._send(message)
    else:
        raise RuntimeError('Cannot call "send" once a close message has been sent.')

accept async 

accept(subprotocol=None, headers=None)
PARAMETER DESCRIPTION
subprotocol

TYPE: str | None DEFAULT: None

headers

TYPE: Iterable[tuple[bytes, bytes]] | None DEFAULT: None

Source code in starlette/websockets.py 
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async def accept(
    self,
    subprotocol: str | None = None,
    headers: typing.Iterable[tuple[bytes, bytes]] | None = None,
) -> None:
    headers = headers or []

    if self.client_state == WebSocketState.CONNECTING:
        # If we haven't yet seen the 'connect' message, then wait for it first.
        await self.receive()
    await self.send({"type": "websocket.accept", "subprotocol": subprotocol, "headers": headers})

receive_text async 

receive_text()
Source code in starlette/websockets.py 
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async def receive_text(self) -> str:
    if self.application_state != WebSocketState.CONNECTED:
        raise RuntimeError('WebSocket is not connected. Need to call "accept" first.')
    message = await self.receive()
    self._raise_on_disconnect(message)
    return typing.cast(str, message["text"])

receive_bytes async 

receive_bytes()
Source code in starlette/websockets.py 
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async def receive_bytes(self) -> bytes:
    if self.application_state != WebSocketState.CONNECTED:
        raise RuntimeError('WebSocket is not connected. Need to call "accept" first.')
    message = await self.receive()
    self._raise_on_disconnect(message)
    return typing.cast(bytes, message["bytes"])

receive_json async 

receive_json(mode='text')
PARAMETER DESCRIPTION
mode

TYPE: str DEFAULT: 'text'

Source code in starlette/websockets.py 
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async def receive_json(self, mode: str = "text") -> typing.Any:
    if mode not in {"text", "binary"}:
        raise RuntimeError('The "mode" argument should be "text" or "binary".')
    if self.application_state != WebSocketState.CONNECTED:
        raise RuntimeError('WebSocket is not connected. Need to call "accept" first.')
    message = await self.receive()
    self._raise_on_disconnect(message)

    if mode == "text":
        text = message["text"]
    else:
        text = message["bytes"].decode("utf-8")
    return json.loads(text)

iter_text async 

iter_text()
Source code in starlette/websockets.py 
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async def iter_text(self) -> typing.AsyncIterator[str]:
    try:
        while True:
            yield await self.receive_text()
    except WebSocketDisconnect:
        pass

iter_bytes async 

iter_bytes()
Source code in starlette/websockets.py 
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async def iter_bytes(self) -> typing.AsyncIterator[bytes]:
    try:
        while True:
            yield await self.receive_bytes()
    except WebSocketDisconnect:
        pass

iter_json async 

iter_json()
Source code in starlette/websockets.py 
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async def iter_json(self) -> typing.AsyncIterator[typing.Any]:
    try:
        while True:
            yield await self.receive_json()
    except WebSocketDisconnect:
        pass

send_text async 

send_text(data)
PARAMETER DESCRIPTION
data

TYPE: str

Source code in starlette/websockets.py 
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async def send_text(self, data: str) -> None:
    await self.send({"type": "websocket.send", "text": data})

send_bytes async 

send_bytes(data)
PARAMETER DESCRIPTION
data

TYPE: bytes

Source code in starlette/websockets.py 
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async def send_bytes(self, data: bytes) -> None:
    await self.send({"type": "websocket.send", "bytes": data})

send_json async 

send_json(data, mode='text')
PARAMETER DESCRIPTION
data

TYPE: Any

mode

TYPE: str DEFAULT: 'text'

Source code in starlette/websockets.py 
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async def send_json(self, data: typing.Any, mode: str = "text") -> None:
    if mode not in {"text", "binary"}:
        raise RuntimeError('The "mode" argument should be "text" or "binary".')
    text = json.dumps(data, separators=(",", ":"), ensure_ascii=False)
    if mode == "text":
        await self.send({"type": "websocket.send", "text": text})
    else:
        await self.send({"type": "websocket.send", "bytes": text.encode("utf-8")})

close async 

close(code=1000, reason=None)
PARAMETER DESCRIPTION
code

TYPE: int DEFAULT: 1000

reason

TYPE: str | None DEFAULT: None

Source code in starlette/websockets.py 
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async def close(self, code: int = 1000, reason: str | None = None) -> None:
    await self.send({"type": "websocket.close", "code": code, "reason": reason or ""})

当客户端断开连接时，会引发一个 WebSocketDisconnect 异常，你可以捕获它。

你可以直接从 fastapi 导入它：

from fastapi import WebSocketDisconnect

fastapi.WebSocketDisconnect 

WebSocketDisconnect(code=1000, reason=None)

Bases: Exception

PARAMETER DESCRIPTION
code

TYPE: int DEFAULT: 1000

reason

TYPE: str | None DEFAULT: None

Source code in starlette/websockets.py 
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def __init__(self, code: int = 1000, reason: str | None = None) -> None:
    self.code = code
    self.reason = reason or ""

code instance-attribute 

code = code

reason instance-attribute 

reason = reason or ''

WebSockets - 附加类

用于处理 WebSockets 的附加类。

由 Starlette 直接提供，但你也可以从 fastapi 导入它：

from fastapi.websockets import WebSocketDisconnect, WebSocketState

fastapi.websockets.WebSocketDisconnect 

WebSocketDisconnect(code=1000, reason=None)

Bases: Exception

PARAMETER DESCRIPTION
code

TYPE: int DEFAULT: 1000

reason

TYPE: str | None DEFAULT: None

Source code in starlette/websockets.py 
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def __init__(self, code: int = 1000, reason: str | None = None) -> None:
    self.code = code
    self.reason = reason or ""

code instance-attribute 

code = code

reason instance-attribute 

reason = reason or ''

fastapi.websockets.WebSocketState

Bases: Enum

CONNECTING class-attribute instance-attribute 

CONNECTING = 0

CONNECTED class-attribute instance-attribute 

CONNECTED = 1

DISCONNECTED class-attribute instance-attribute 

DISCONNECTED = 2

RESPONSE class-attribute instance-attribute 

RESPONSE = 3