WebSocket PureBasic Reference Documentation

WebSocket

Current Version: 11.5.0

Chilkat.WebSocket

Connect to WebSocket servers and exchange client-side frames and messages.

Client-side only: Chilkat.WebSocket implements the client side of the WebSocket protocol. It initiates an opening handshake with an existing WebSocket server. It does not listen for incoming connections, accept clients, or implement a WebSocket server.

Chilkat.WebSocket operates over an established Chilkat.Rest connection. It creates and validates the HTTP upgrade handshake, sends and receives text or binary frames, supports fragmented messages, handles Ping, Pong, and Close control frames, polls for incoming data, and exposes frame-level diagnostics.

Client opening handshake

Upgrade a connected Rest session to WebSocket and validate the server's response before exchanging frames.

Text and binary messages

Send UTF-8 text or exact binary bytes as single-frame or fragmented WebSocket messages.

Frame-by-frame receiving

Read frames, inspect opcodes and the FIN state, and accumulate fragments until a complete message is available.

Ping and Pong

Use automatic or manual control-frame handling for keep-alive and responsiveness checks.

Clean close handshake

Exchange Close frames, inspect the peer's status code and reason, and terminate the underlying connection cleanly.

Separate read/write paths

Share a connection between two WebSocket objects when one thread needs to read while another writes.

Typical connection sequence: Connect a Rest object to the server, call UseConnection, call AddClientHeaders, send the opening HTTP GET request through Rest, and then call ValidateServerHandshake. Only after validation succeeds should the application call frame send/receive methods.
Frames versus messages: A WebSocket message may consist of one frame or several fragments. When receiving a fragmented message, call ReadFrame until FinalFrame is 1, then retrieve the accumulated data with GetFrameData, GetFrameDataSb, or GetFrameDataBd.

Object Creation

obj.i = CkWebSocket::ckCreate()

; Make sure to dispose of the object when finished like this:
CkWebSocket::ckDispose(obj);

Properties

CloseAutoRespond
Declare.i ckCloseAutoRespond(obj.i)
Declare setCkCloseAutoRespond(obj.i, value.i)
Introduced in version 9.5.0.70

Controls whether Chilkat automatically answers an incoming Close control frame.

  • When 1, an incoming Close is answered automatically if the client did not already initiate the close. After a Close has been both received and sent, Chilkat closes the underlying connection.
  • When 0, the application can detect the received Close through CloseReceived or FrameOpcode and call SendClose itself.

The default is 1.

Closing handshake: A peer that receives a Close and has not already sent one should respond with a Close. Automatic response is usually the safest choice unless the application must control the exact status code or timing.

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CloseReason
Declare.s ckCloseReason(obj.i) ; (read-only)
Introduced in version 9.5.0.70

Returns the UTF-8 reason text contained in the received Close control frame.

The value is empty when the peer supplied no reason or when no Close frame has been received. A reason is diagnostic text and should not be treated as a stable machine-readable error identifier; use CloseStatusCode for protocol-level handling.

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CloseReceived
Declare.i ckCloseReceived(obj.i) ; (read-only)
Introduced in version 9.5.0.70

1 after a Close control frame has been received on the current WebSocket connection.

When CloseAutoRespond is 0, use this property to determine whether the application needs to call SendClose to complete the closing handshake. The received status code and reason, if present, are available through CloseStatusCode and CloseReason.

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CloseStatusCode
Declare.i ckCloseStatusCode(obj.i) ; (read-only)
Introduced in version 9.5.0.70

Returns the status code contained in the received Close control frame.

Returns 0 when no Close frame has been received or when the received Close frame did not include a status code.

Meaning of zero: 0 is an API sentinel; it is not a WebSocket close status transmitted by the peer.

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DebugLogFilePath
Declare.s ckDebugLogFilePath(obj.i)
Declare setCkDebugLogFilePath(obj.i, value.s)

If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. This logging helps identify the context and history of Chilkat calls leading up to any crash or hang, aiding in debugging.

Enabling the VerboseLogging property provides more detailed information. This property is mainly used for debugging rare instances where a Chilkat method call causes a hang or crash, which should generally not happen.

Possible causes of hangs include:

  • A timeout property set to 0, indicating an infinite timeout.
  • A hang occurring within an event callback in the application code.
  • An internal bug in the Chilkat code causing the hang.

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FinalFrame
Declare.i ckFinalFrame(obj.i) ; (read-only)
Introduced in version 9.5.0.70

1 if the frame most recently delivered by ReadFrame had its WebSocket FIN bit set; otherwise 0.

For a fragmented data message, continue reading while this property is 0. The fragment with 1 completes the message. Unfragmented messages have 1 on their only frame.

Control frames: Close, Ping, and Pong are control frames and are not fragmented by the WebSocket protocol; their FIN bit is always set.

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FrameDataLen
Declare.i ckFrameDataLen(obj.i) ; (read-only)
Introduced in version 9.5.0.70

Returns the number of payload bytes currently accumulated in the internal receive buffer.

The value can represent data from one frame or from multiple calls to ReadFrame, which is useful when receiving a fragmented message. The accumulated bytes remain available until retrieved by GetFrameData, GetFrameDataSb, or GetFrameDataBd.

Message length: This is the length accumulated so far, not necessarily the final length of the complete WebSocket message. Check FinalFrame to determine whether the last received fragment completed the message.

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FrameOpcode
Declare.s ckFrameOpcode(obj.i) ; (read-only)
Introduced in version 9.5.0.70

Returns the symbolic opcode of the frame most recently delivered by ReadFrame.

ValueMeaning
ContinuationA later fragment of a Text or Binary message
TextUTF-8 text data
BinaryBinary data
CloseClosing handshake
PingPing control frame
PongPong control frame

Before any frame has been received, the value is the empty string. Ping or Pong frames handled internally by the auto-response/auto-consume options may not be returned as the current frame.

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FrameOpcodeInt
Declare.i ckFrameOpcodeInt(obj.i) ; (read-only)
Introduced in version 9.5.0.70

Returns the numeric opcode of the frame most recently delivered by ReadFrame.

ValueFrame type
0Continuation
1Text
2Binary
8Close
9Ping
10Pong

Use FrameOpcode when a readable symbolic value is preferred.

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IdleTimeoutMs
Declare.i ckIdleTimeoutMs(obj.i)
Declare setCkIdleTimeoutMs(obj.i, value.i)

Specifies the maximum number of milliseconds an active send or receive operation may remain stalled while waiting for additional network progress.

The default is 30000 milliseconds (30 seconds). This is an inactivity timeout, not a total limit on the duration of the operation. An operation may continue longer than this value as long as data continues to be transferred.

Not a keep-alive interval: This property does not automatically send WebSocket Ping frames. Use SendPing when the application needs protocol-level keep-alive or responsiveness checks.

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IsConnected
Declare.i ckIsConnected(obj.i) ; (read-only)
Introduced in version 9.5.0.70

1 when the underlying WebSocket network connection is currently open; otherwise 0.

Connection state is not a health check: A network interruption may not be detected until the next read or write operation. Use normal I/O results—and optionally Ping/Pong—to determine whether a seemingly connected peer is still responsive.

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LastErrorHtml
Declare.s ckLastErrorHtml(obj.i) ; (read-only)

Provides HTML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastErrorText
Declare.s ckLastErrorText(obj.i) ; (read-only)

Provides plain text information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastErrorXml
Declare.s ckLastErrorXml(obj.i) ; (read-only)

Provides XML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastMethodSuccess
Declare.i ckLastMethodSuccess(obj.i)
Declare setCkLastMethodSuccess(obj.i, value.i)

Indicates the success or failure of the most recent method call: 1 means success, 0 means failure. This property remains unchanged by property setters or getters. This method is present to address challenges in checking for null or Nothing returns in certain programming languages. Note: This property does not apply to methods that return integer values or to boolean-returning methods where the boolean does not indicate success or failure.

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NeedSendPong
Declare.i ckNeedSendPong(obj.i) ; (read-only)
Introduced in version 9.5.0.70

1 when a Ping frame has been received but no corresponding Pong has yet been sent.

This property is primarily useful when PingAutoRespond is 0. Call SendPong as soon as practical; it automatically sends the received Ping payload in the Pong response.

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PingAutoRespond
Declare.i ckPingAutoRespond(obj.i)
Declare setCkPingAutoRespond(obj.i, value.i)
Introduced in version 9.5.0.70

Controls automatic handling of incoming Ping control frames.

  • When 1, Chilkat sends the required Pong automatically and ReadFrame consumes the Ping internally, continuing until another frame is available.
  • When 0, the Ping can be returned to the application. Check NeedSendPong and call SendPong as soon as practical.

The default is 1.

Payload echo: A Pong sent in response to a Ping must carry the same application data. SendPong automatically uses the stored payload of the unanswered Ping.

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PongAutoConsume
Declare.i ckPongAutoConsume(obj.i)
Declare setCkPongAutoConsume(obj.i, value.i)
Introduced in version 9.5.0.70

Controls whether incoming Pong control frames are hidden from the application.

  • When 1, ReadFrame consumes Pong frames internally and continues reading until a non-Pong frame is available.
  • When 0, an incoming Pong can be returned normally with FrameOpcode equal to Pong.

The default is 1. Check PongConsumed after ReadFrame to learn whether one or more Pong frames were consumed during that call.

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PongConsumed
Declare.i ckPongConsumed(obj.i) ; (read-only)
Introduced in version 9.5.0.70

1 if the most recent call to ReadFrame internally consumed a Pong frame while PongAutoConsume was 1.

The property is reset to 0 at the beginning of each ReadFrame call and set to 1 if a Pong is consumed during that call.

Why unsolicited Pong is possible: Either endpoint may send a Pong without a preceding Ping, and a response to an earlier Ping may arrive between application data frames. Automatic consumption allows ordinary read loops to ignore these control frames while still detecting that they occurred.

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ReadFrameFailReason
Declare.i ckReadFrameFailReason(obj.i) ; (read-only)
Introduced in version 9.5.0.70

When ReadFrame returns 0, this property categorizes the reason:

ValueMeaning
0No failure is recorded
1Read inactivity timeout
2Aborted by an application callback
3Fatal socket error or lost connection
4Invalid WebSocket frame bytes were received
99Unexpected catch-all failure

Use this value for programmatic branching and inspect LastErrorText for detailed diagnostics.

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UncommonOptions
Declare.s ckUncommonOptions(obj.i) ; (read-only)
Introduced in version 9.5.0.80

Contains a comma-separated list of rarely needed compatibility or platform options. The default is the empty string and should normally remain unchanged.

KeywordEffect
ProtectFromVpnOn Android, attempts to route the connection outside an installed or active VPN. Introduced in v9.5.0.80.
Platform-specific behavior: This option applies only on Android. Leave the property empty on other platforms and unless bypassing the device VPN is an explicit application requirement.

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VerboseLogging
Declare.i ckVerboseLogging(obj.i)
Declare setCkVerboseLogging(obj.i, value.i)

If set to 1, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is 0. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

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Version
Declare.s ckVersion(obj.i) ; (read-only)

Version of the component/library, such as "10.1.0"

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Methods

AddClientHeaders
Declare.i ckAddClientHeaders(obj.i)
Introduced in version 9.5.0.70

Adds the standard client opening-handshake headers to the Rest object supplied to UseConnection:

Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: ...
Sec-WebSocket-Version: 13

Sec-WebSocket-Key contains a newly generated client nonce used by the server to produce Sec-WebSocket-Accept.

Additional handshake headers: If the server requires headers such as Origin, Authorization, cookies, or Sec-WebSocket-Protocol, add them through the associated Rest object before sending the HTTP upgrade request.

Returns 1 for success, 0 for failure.

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CloseConnection
Declare.i ckCloseConnection(obj.i)
Introduced in version 9.5.0.70

Immediately closes the underlying network connection without completing the WebSocket closing handshake.

Use this method when the connection must be abandoned because of a fatal error, timeout, application shutdown, or an unresponsive peer.

Preferred shutdown: For a normal shutdown, call SendClose, receive the peer's Close frame with ReadFrame, and allow the closing handshake to complete. An abrupt transport close does not provide the peer with a WebSocket status code or reason.

Returns 1 for success, 0 for failure.

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GetFrameData
Declare.s ckGetFrameData(obj.i)
Introduced in version 9.5.0.70

Returns the bytes accumulated by successful calls to ReadFrame as a string, then clears the internal receive buffer.

This method is intended for WebSocket text-message data. For arbitrary binary payloads, use GetFrameDataBd to avoid interpreting binary bytes as text.

Fragmented messages: To retrieve an entire fragmented message, continue calling ReadFrame until FinalFrame is 1, and then call GetFrameData once. Calling this method earlier returns and clears only the data accumulated so far.

Returns an empty string on failure. Use the LastMethodSuccess property to check for success.

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GetFrameDataBd
Declare.i ckGetFrameDataBd(obj.i, binData.i)
Introduced in version 9.5.0.70

Appends the bytes accumulated by successful calls to ReadFrame to binData, then clears the internal receive buffer.

Use this method for binary messages or whenever the exact received bytes must be preserved. Existing data in the destination BinData is retained because the received bytes are appended.

Receive-buffer ownership: Calling any one of GetFrameData, GetFrameDataSb, or GetFrameDataBd consumes the same internal buffer. Retrieve the data using only the form needed by the application.
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GetFrameDataSb
Declare.i ckGetFrameDataSb(obj.i, sb.i)
Introduced in version 9.5.0.70

Appends the text represented by the bytes accumulated by successful calls to ReadFrame to sb, then clears the internal receive buffer.

Existing text in the destination StringBuilder is retained. This method is most appropriate for text-message data; use GetFrameDataBd for arbitrary binary payloads.

Fragmented messages: The receive buffer can accumulate multiple frames. Read until FinalFrame is 1 before calling this method when the application wants the complete message.
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LoadTaskCaller
Declare.i ckLoadTaskCaller(obj.i, task.i)
Introduced in version 9.5.0.80

Loads the caller object associated with an asynchronous Task method invocation.

This is used by Chilkat's asynchronous task infrastructure when access to the original WebSocket object is required after the task completes.

Returns 1 for success, 0 for failure.

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PollDataAvailable
Declare.i ckPollDataAvailable(obj.i)
Introduced in version 9.5.0.70

Checks whether bytes are currently waiting to be read from the underlying WebSocket connection.

Returns 1 when incoming data is available and 0 when no data is presently waiting.

Polling is only a snapshot: A 1 result does not mean that an entire WebSocket frame or message has arrived. Call ReadFrame to parse the protocol frame. A 0 result does not indicate that the peer will not send data later.
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ReadFrame
Declare.i ckReadFrame(obj.i)
Introduced in version 9.5.0.70

Reads the next WebSocket frame from the connected server. On success, the method updates FrameOpcode, FrameOpcodeInt, FinalFrame, and FrameDataLen.

Frame payload bytes are added to an internal receive buffer. The buffer may therefore contain data accumulated by multiple calls to ReadFrame. Retrieve and clear it with GetFrameData, GetFrameDataSb, or GetFrameDataBd.

Reading a complete message

Call ReadFrame until FinalFrame is 1, then retrieve the accumulated message data. A fragmented message begins with a Text or Binary frame and continues with one or more Continuation frames.

Control-frame automation: Depending on PingAutoRespond and PongAutoConsume, incoming Ping and Pong frames may be handled internally, causing this method to continue reading until another frame is available. If the method returns 0, inspect ReadFrameFailReason and LastErrorText.

Returns 1 for success, 0 for failure.

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ReadFrameAsync (1)
Declare.i ckReadFrameAsync(obj.i)
Introduced in version 9.5.0.70

Creates an asynchronous task to call the ReadFrame method with the arguments provided.

Returns 0 on failure

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SendClose
Declare.i ckSendClose(obj.i, includeStatus.l, statusCode.l, reason.s)
Introduced in version 9.5.0.70

Sends a WebSocket Close control frame and begins or completes the closing handshake.

  • If includeStatus is 0, the Close frame contains no status code and statusCode and reason are ignored.
  • If includeStatus is 1, the frame contains statusCode followed by the UTF-8 bytes of reason.

The complete Close payload cannot exceed 125 bytes, leaving at most 123 bytes for the UTF-8 reason after the two-byte status code. Chilkat truncates an overlong reason. The API accepts status-code integers from 0 through 16383.

Protocol-valid status codes: The API's numeric range is broader than the set valid for transmission under RFC 6455. Use a defined protocol code such as 1000 for normal closure, or an appropriate application code in the 30004999 range. Codes 1005, 1006, and 1015 are reserved reporting values and must not be sent in a Close frame.
Clean close: After initiating a close, read the peer's Close response. If this method answers a Close already received from the server, Chilkat also closes the underlying connection after sending the response.

Returns 1 for success, 0 for failure.

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SendCloseAsync (1)
Declare.i ckSendCloseAsync(obj.i, includeStatus.l, statusCode.l, reason.s)
Introduced in version 9.5.0.70

Creates an asynchronous task to call the SendClose method with the arguments provided.

Returns 0 on failure

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SendFrame
Declare.i ckSendFrame(obj.i, stringToSend.s, finalFrame.l)
Introduced in version 9.5.0.70

Sends one WebSocket text data frame containing stringToSend. WebSocket text data is UTF-8 on the wire.

  • Set finalFrame to 1 when this frame completes the message.
  • Set finalFrame to 0 when additional frames will follow as part of the same fragmented message.

For a normal unfragmented text message, call this method once with finalFrame set to 1. For a fragmented message, call it repeatedly and set 1 only for the final fragment.

Frames and messages: A WebSocket message may contain one frame or multiple fragments. Do not begin a second data message until the current fragmented message has been completed. Control frames such as Ping, Pong, and Close may occur between message fragments.

Returns 1 for success, 0 for failure.

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SendFrameAsync (1)
Declare.i ckSendFrameAsync(obj.i, stringToSend.s, finalFrame.l)
Introduced in version 9.5.0.70

Creates an asynchronous task to call the SendFrame method with the arguments provided.

Returns 0 on failure

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SendFrameBd
Declare.i ckSendFrameBd(obj.i, bdToSend.i, finalFrame.l)
Introduced in version 9.5.0.70

Sends one WebSocket binary data frame containing the current bytes in bdToSend.

  • Set finalFrame to 1 when this frame completes the binary message.
  • Set finalFrame to 0 when additional binary-message fragments will follow.

For an ordinary single-frame binary message, set finalFrame to 1.

Exact bytes: No text encoding is involved. The bytes stored in bdToSend become the frame payload, while Chilkat applies the client-side WebSocket framing and masking required by the protocol.

Returns 1 for success, 0 for failure.

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SendFrameBdAsync (1)
Declare.i ckSendFrameBdAsync(obj.i, bdToSend.i, finalFrame.l)
Introduced in version 9.5.0.70

Creates an asynchronous task to call the SendFrameBd method with the arguments provided.

Returns 0 on failure

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SendFrameSb
Declare.i ckSendFrameSb(obj.i, sbToSend.i, finalFrame.l)
Introduced in version 9.5.0.70

Sends one WebSocket text data frame containing the current contents of sbToSend.

  • Set finalFrame to 1 when this frame completes the message.
  • Set finalFrame to 0 when more fragments will follow.

For an ordinary single-frame text message, set finalFrame to 1. WebSocket text data is UTF-8 on the wire.

Message fragmentation: Repeated calls with finalFrame set to 0 create fragments of the same text message. Complete the message with a final call that passes 1.

Returns 1 for success, 0 for failure.

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SendFrameSbAsync (1)
Declare.i ckSendFrameSbAsync(obj.i, sbToSend.i, finalFrame.l)
Introduced in version 9.5.0.70

Creates an asynchronous task to call the SendFrameSb method with the arguments provided.

Returns 0 on failure

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SendPing
Declare.i ckSendPing(obj.i, pingData.s)
Introduced in version 9.5.0.70

Sends a WebSocket Ping control frame. If pingData is non-empty, its UTF-8 bytes are included as the Ping payload.

WebSocket control-frame payloads are limited to 125 bytes. If the UTF-8 representation exceeds this limit, Chilkat truncates it to 125 bytes.

Ping/Pong behavior: A peer that receives a Ping is expected to send a Pong containing the same application data as soon as practical. Ping is useful for protocol-level liveness checks, but receiving a Pong does not by itself prove that the application running above the connection is healthy.

Returns 1 for success, 0 for failure.

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SendPingAsync (1)
Declare.i ckSendPingAsync(obj.i, pingData.s)
Introduced in version 9.5.0.70

Creates an asynchronous task to call the SendPing method with the arguments provided.

Returns 0 on failure

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SendPong
Declare.i ckSendPong(obj.i)
Introduced in version 9.5.0.70

Sends a WebSocket Pong control frame.

When a Ping has been received and has not yet been answered, this method automatically uses the previously received Ping payload as the Pong payload, as required for a Ping response.

Manual response mode: This method is normally used when PingAutoRespond is 0 and NeedSendPong is 1. When automatic Ping handling is enabled, Chilkat sends the Pong internally.

Returns 1 for success, 0 for failure.

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SendPongAsync (1)
Declare.i ckSendPongAsync(obj.i)
Introduced in version 9.5.0.70

Creates an asynchronous task to call the SendPong method with the arguments provided.

Returns 0 on failure

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ShareConnection
Declare.i ckShareConnection(obj.i, ws.i)
Introduced in version 11.0.0

Causes the calling WebSocket object to share the already-established WebSocket connection owned by ws.

This enables a bidirectional design in which separate WebSocket objects operate on the same connection—for example, one thread blocks in ReadFrame while another thread sends frames.

Concurrency model: Use this feature to separate the read path from the write path. The application remains responsible for coordinating object lifetime, shutdown, and higher-level message state. Avoid multiple concurrent readers or multiple unsynchronized writers unless the application provides its own coordination.

Returns 1 for success, 0 for failure.

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UseConnection
Declare.i ckUseConnection(obj.i, connection.i)
Introduced in version 9.5.0.70

Associates this WebSocket object with an existing, connected Rest object and prepares it for a client-side WebSocket session.

The opening WebSocket handshake is an HTTP GET upgrade request. Using Rest for the underlying connection allows the application to configure TLS, proxies, authentication, custom request headers, IPv6, socket options, bandwidth limits, and other connection features before the upgrade is performed.

Client-side API: Chilkat.WebSocket initiates connections to WebSocket servers. It does not listen for incoming connections or implement a WebSocket server endpoint.
Typical opening sequence
  1. Connect the Rest object to the server.
  2. Call UseConnection.
  3. Call AddClientHeaders.
  4. Send the HTTP GET request with the Rest object.
  5. Call ValidateServerHandshake.

Returns 1 for success, 0 for failure.

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ValidateServerHandshake
Declare.i ckValidateServerHandshake(obj.i)
Introduced in version 9.5.0.70

Validates the server's response to the WebSocket opening handshake sent through the associated Rest object.

Validation checks that the server accepted the HTTP upgrade and returned the expected WebSocket handshake response, including the value derived from the client's Sec-WebSocket-Key. If this method returns 1, the connection has entered the WebSocket protocol and data or control frames may be exchanged.

Call order: Call this method only after the Rest object has sent the opening GET request and received the server's response. A successful HTTP request alone does not establish a WebSocket session; the response must also pass this validation.

Returns 1 for success, 0 for failure.

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