Client (threading) - websockets 12.0 documentation
Description: Opening a connection: Using a connection:

Hide navigation sidebar
Hide table of contents sidebar
Back to top
Toggle table of contents sidebar

# Client (`threading`)

## Opening a connection

websockets.sync.client.connect(uri, *, sock=None, ssl_context=None, server_hostname=None, origin=None, extensions=None, subprotocols=None, additional_headers=None, user_agent_header='Python/x.y.z websockets/X.Y', compression='deflate', open_timeout=10, close_timeout=10, max_size=2**20, logger=None, create_connection=None)

  Connect to the WebSocket server at `uri`.

  This function returns a `ClientConnection` instance, which you can use to send and receive messages.

  `connect()` may be used as a context manager:

      async with websockets.sync.client.connect(...) as websocket:
          ...

  The connection is closed automatically when exiting the context.

  Parameters:

    - uri (str) – URI of the WebSocket server.

    - sock (socket | None) – Preexisting TCP socket. `sock` overrides the host and port from `uri`. You may call `socket.create_connection()` to create a suitable TCP socket.

    - ssl_context (SSLContext | None) – Configuration for enabling TLS on the connection.

    - server_hostname (str | None) – Host name for the TLS handshake. `server_hostname` overrides the host name from `uri`.

    - origin (Origin | None) – Value of the `Origin` header, for servers that require it.

    - extensions (Sequence[ClientExtensionFactory] | None) – List of supported extensions, in order in which they should be negotiated and run.

    - subprotocols (Sequence[Subprotocol] | None) – List of supported subprotocols, in order of decreasing preference.

    - additional_headers (HeadersLike | None) – Arbitrary HTTP headers to add to the handshake request.

    - user_agent_header (str | None) – Value of the `User-Agent` request header. It defaults to `"Python/x.y.z websockets/X.Y"`. Setting it to `None` removes the header.

    - compression (str | None) – The “permessage-deflate” extension is enabled by default. Set `compression` to `None` to disable it. See the compression guide for details.

    - open_timeout (float | None) – Timeout for opening the connection in seconds. `None` disables the timeout.

    - close_timeout (float | None) – Timeout for closing the connection in seconds. `None` disables the timeout.

    - max_size (int | None) – Maximum size of incoming messages in bytes. `None` disables the limit.

    - logger (Logger | LoggerAdapter | None) – Logger for this client. It defaults to `logging.getLogger("websockets.client")`. See the logging guide for details.

    - create_connection (Type[ClientConnection] | None) – Factory for the `ClientConnection` managing the connection. Set it to a wrapper or a subclass to customize connection handling.

  Raises:

    - InvalidURI – If `uri` isn’t a valid WebSocket URI.

    - OSError – If the TCP connection fails.

    - InvalidHandshake – If the opening handshake fails.

    - TimeoutError – If the opening handshake times out.

websockets.sync.client.unix_connect(path, uri=None, *, sock=None, ssl_context=None, server_hostname=None, origin=None, extensions=None, subprotocols=None, additional_headers=None, user_agent_header='Python/x.y.z websockets/X.Y', compression='deflate', open_timeout=10, close_timeout=10, max_size=2**20, logger=None, create_connection=None)

  Connect to a WebSocket server listening on a Unix socket.

  This function is identical to `connect()`, except for the additional `path` argument. It’s only available on Unix.

  It’s mainly useful for debugging servers listening on Unix sockets.

  Parameters:

    - path (str | None) – File system path to the Unix socket.

    - uri (str | None) – URI of the WebSocket server. `uri` defaults to `ws://localhost/` or, when a `ssl_context` is provided, to `wss://localhost/`.

## Using a connection

class websockets.sync.client.ClientConnection(socket, protocol, *, close_timeout=10)

  Threaded implementation of a WebSocket client connection.

  `ClientConnection` provides `recv()` and `send()` methods for receiving and sending messages.

  It supports iteration to receive messages:

      for message in websocket:
          process(message)

  The iterator exits normally when the connection is closed with close code 1000 (OK) or 1001 (going away) or without a close code. It raises a `ConnectionClosedError` when the connection is closed with any other code.

  Parameters:

    - socket (socket.socket) – Socket connected to a WebSocket server.

    - protocol (ClientProtocol) – Sans-I/O connection.

    - close_timeout (Optional[float]) – Timeout for closing the connection in seconds.

  for ... in __iter__()

    Iterate on incoming messages.

    The iterator calls `recv()` and yields messages in an infinite loop.

    It exits when the connection is closed normally. It raises a `ConnectionClosedError` exception after a protocol error or a network failure.

  recv(timeout=None)

    Receive the next message.

    When the connection is closed, `recv()` raises `ConnectionClosed`. Specifically, it raises `ConnectionClosedOK` after a normal closure and `ConnectionClosedError` after a protocol error or a network failure. This is how you detect the end of the message stream.

    If `timeout` is `None`, block until a message is received. If `timeout` is set and no message is received within `timeout` seconds, raise `TimeoutError`. Set `timeout` to `0` to check if a message was already received.

    If the message is fragmented, wait until all fragments are received, reassemble them, and return the whole message.

    Returns:

      A string (`str`) for a Text frame or a bytestring (`bytes`) for a Binary frame.

    Raises:

      - ConnectionClosed – When the connection is closed.

      - RuntimeError – If two threads call `recv()` or `recv_streaming()` concurrently.

    Return type:

      str | bytes

  for ... in recv_streaming()

    Receive the next message frame by frame.

    If the message is fragmented, yield each fragment as it is received. The iterator must be fully consumed, or else the connection will become unusable.

    `recv_streaming()` raises the same exceptions as `recv()`.

    Returns:

      An iterator of strings (`str`) for a Text frame or bytestrings (`bytes`) for a Binary frame.

    Raises:

      - ConnectionClosed – When the connection is closed.

      - RuntimeError – If two threads call `recv()` or `recv_streaming()` concurrently.

    Return type:

      Iterator[str | bytes]

  send(message)

    Send a message.

    A string (`str`) is sent as a Text frame. A bytestring or bytes-like object (`bytes`, `bytearray`, or `memoryview`) is sent as a Binary frame.

    `send()` also accepts an iterable of strings, bytestrings, or bytes-like objects to enable fragmentation. Each item is treated as a message fragment and sent in its own frame. All items must be of the same type, or else `send()` will raise a `TypeError` and the connection will be closed.

    `send()` rejects dict-like objects because this is often an error. (If you really want to send the keys of a dict-like object as fragments, call its `keys()` method and pass the result to `send()`.)

    When the connection is closed, `send()` raises `ConnectionClosed`. Specifically, it raises `ConnectionClosedOK` after a normal connection closure and `ConnectionClosedError` after a protocol error or a network failure.

    Parameters:

      message (str | bytes | Iterable[str | bytes]) – Message to send.

    Raises:

      - ConnectionClosed – When the connection is closed.

      - RuntimeError – If a connection is busy sending a fragmented message.

      - TypeError – If `message` doesn’t have a supported type.

  close(code=CloseCode.NORMAL_CLOSURE, reason='')

    Perform the closing handshake.

    `close()` waits for the other end to complete the handshake, for the TCP connection to terminate, and for all incoming messages to be read with `recv()`.

    `close()` is idempotent: it doesn’t do anything once the connection is closed.

    Parameters:

      - code (int) – WebSocket close code.

      - reason (str) – WebSocket close reason.

  ping(data=None)

    Send a Ping.

    A ping may serve as a keepalive or as a check that the remote endpoint received all messages up to this point

    Parameters:

      data (str | bytes | None) – Payload of the ping. A `str` will be encoded to UTF-8. If `data` is `None`, the payload is four random bytes.

    Returns:

      An event that will be set when the corresponding pong is received. You can ignore it if you don’t intend to wait.

          pong_event = ws.ping()
          pong_event.wait()  # only if you want to wait for the pong

    Raises:

      - ConnectionClosed – When the connection is closed.

      - RuntimeError – If another ping was sent with the same data and the corresponding pong wasn’t received yet.

    Return type:

      Event

  pong(data=b'')

    Send a Pong.

    An unsolicited pong may serve as a unidirectional heartbeat.

    Parameters:

      data (str | bytes) – Payload of the pong. A `str` will be encoded to UTF-8.

    Raises:

      ConnectionClosed – When the connection is closed.

  WebSocket connection objects also provide these attributes:

  id: uuid.UUID

    Unique identifier of the connection. Useful in logs.

  logger: LoggerLike

    Logger for this connection.

  property local_address: Any

    Local address of the connection.

    For IPv4 connections, this is a `(host, port)` tuple.

    The format of the address depends on the address family. See `getsockname()`.

  property remote_address: Any

    Remote address of the connection.

    For IPv4 connections, this is a `(host, port)` tuple.

    The format of the address depends on the address family. See `getpeername()`.

  The following attributes are available after the opening handshake, once the WebSocket connection is open:

  request: Request | None

    Opening handshake request.

  response: Response | None

    Opening handshake response.

  property subprotocol: Subprotocol | None

    Subprotocol negotiated during the opening handshake.

    `None` if no subprotocol was negotiated.