WebSocket C Reference Documentation
WebSocket
Current Version: 10.0.0
Provides an API for implementing the client side of the WebSocket protocol.
Create/Dispose
HCkWebSocket instance = CkWebSocket_Create(); // ... CkWebSocket_Dispose(instance);
Creates an instance of the HCkWebSocket object and returns a handle ("void *" pointer). The handle is passed in the 1st argument for the functions listed on this page.
Objects created by calling CkWebSocket_Create must be freed by calling this method. A memory leak occurs if a handle is not disposed by calling this function. Also, any handle returned by a Chilkat "C" function must also be freed by the application by calling the appropriate Dispose method, such as CkWebSocket_Dispose.
Callback Functions
Provides the opportunity for a method call to be aborted. If TRUE is returned, the operation in progress is aborted. Return FALSE to allow the current method call to continue. This callback function is called periodically based on the value of the HeartbeatMs property. (If HeartbeatMs is 0, then no callbacks are made.) As an example, to make 5 AbortCheck callbacks per second, set the HeartbeatMs property equal to 200.
See Also:C Example using Callback Functions
Provides the percentage completed for any method that involves network communications or time-consuming processing (assuming it is a method where a percentage completion can be measured). This callback is only called when it is possible to know a percentage completion, and when it makes sense to express the operation as a percentage completed. The pctDone argument will have a value from 1 to 100. For methods that complete very quickly, the number of PercentDone callbacks will vary, but the final callback should have a value of 100. For long running operations, no more than one callback per percentage point will occur (for example: 1, 2, 3, ... 98, 99, 100).
This callback counts as an AbortCheck callback, and takes the place of the AbortCheck event when it fires.
The return value indicates whether the method call should be aborted, or whether it should proceed. Return TRUE to abort, and FALSE to proceed.
This is a general callback that provides name/value information about what is happening at certain points during a method call. To see the information provided in ProgressInfo callbacks, if any, write code to handle this event and log the name/value pairs. Most are self-explanatory.
Called in the background thread when an asynchronous task completes. (Note: When an async method is running, all callbacks are in the background thread.)
Properties
CloseAutoRespond
void CkWebSocket_putCloseAutoRespond(HCkWebSocket cHandle, BOOL newVal);
If TRUE, then a Close control frame is automatically sent in response to receiving a Close control frame (assuming that we did not initiate the Close in the first place). When the Close frame has both been received and sent, the underlying connection is automatically closed (as per the WebSocket protocol RFC specifications). Thus, if this property is TRUE, then two things automatically happen when a Close frame is received: (1) a Close frame is sent in response, and (2) the connection is closed.
The default value of this property is TRUE.
topCloseReason
const char *CkWebSocket_closeReason(HCkWebSocket cHandle);
The reason string received with the Close frame, if any.
topCloseReceived
If TRUE, then a Close frame was already received on this websocket connection. If CloseAutoRespond is FALSE, then an application can check this property value to determine if a Close frame should be sent in response.
topCloseStatusCode
The status code received with the Close frame. If no status code was provided, or no Close frame has yet been received, then this property will be 0.
topDebugLogFilePath
void CkWebSocket_putDebugLogFilePath(HCkWebSocket cHandle, const char *newVal);
const char *CkWebSocket_debugLogFilePath(HCkWebSocket cHandle);
If set to a file path, causes each Chilkat method or property call to automatically append it's LastErrorText to the specified log file. The information is appended such that if a hang or crash occurs, it is possible to see the context in which the problem occurred, as well as a history of all Chilkat calls up to the point of the problem. The VerboseLogging property can be set to provide more detailed information.
This property is typically used for debugging the rare cases where a Chilkat method call hangs or generates an exception that halts program execution (i.e. crashes). A hang or crash should generally never happen. The typical causes of a hang are:
- a timeout related property was set to 0 to explicitly indicate that an infinite timeout is desired,
- the hang is actually a hang within an event callback (i.e. it is a hang within the application code), or
- there is an internal problem (bug) in the Chilkat code that causes the hang.
FinalFrame
TRUE if the last data frame received by calling ReadFrame was a final frame. Otherwise FALSE.
topFrameDataLen
The number of bytes accumulated from one or more calls to ReadFrame. Accumulated incoming frame data can be retrieved by calling GetFrameData, GetFrameDataSb, or GetFrameDataBd.
topFrameOpcode
const char *CkWebSocket_frameOpcode(HCkWebSocket cHandle);
Indicates the type of frame received in the last call to ReadFrame. Possible values are "Continuation", "Text", "Binary", "Close", "Ping", or "Pong". Initially this property is set to the empty string because nothing has yet been received.
topFrameOpcodeInt
The integer value of the opcode (type of frame) received in the last call to ReadFrame. Possible values are:
0 - Continuation 1 - Text 2 - Binary 8 - Close 9 - Ping 10 - Pongtop
HeartbeatMs
void CkWebSocket_putHeartbeatMs(HCkWebSocket cHandle, int newVal);
The time interval, in milliseconds, between AbortCheck event callbacks. The heartbeat provides a means for an application to monitor a method call that has event callbacks, and to abort it while in progress.
topIdleTimeoutMs
void CkWebSocket_putIdleTimeoutMs(HCkWebSocket cHandle, int newVal);
The maximum amount of time to wait for additional incoming data when receiving, or the max time to wait to send additional data. The default value is 30000 (30 seconds). This is not an overall max timeout. Rather, it is the maximum time to wait when receiving or sending has halted.
topIsConnected
Returns TRUE if the websocket is connected. Otherwise returns FALSE.
topLastErrorHtml
const char *CkWebSocket_lastErrorHtml(HCkWebSocket cHandle);
Provides information in HTML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.
topLastErrorText
const char *CkWebSocket_lastErrorText(HCkWebSocket cHandle);
Provides information in plain-text format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.
LastErrorXml
const char *CkWebSocket_lastErrorXml(HCkWebSocket cHandle);
Provides information in XML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.
topLastMethodSuccess
void CkWebSocket_putLastMethodSuccess(HCkWebSocket cHandle, BOOL newVal);
Indicate whether the last method call succeeded or failed. A value of TRUE indicates success, a value of FALSE indicates failure. This property is automatically set for method calls. It is not modified by property accesses. The property is automatically set to indicate success for the following types of method calls:
- Any method that returns a string.
- Any method returning a Chilkat object, binary bytes, or a date/time.
- Any method returning a standard boolean status value where success = TRUE and failure = FALSE.
- Any method returning an integer where failure is defined by a return value less than zero.
Note: Methods that do not fit the above requirements will always set this property equal to TRUE. For example, a method that returns no value (such as a "void" in C++) will technically always succeed.
topNeedSendPong
If TRUE, then a Ping frame was received, but no Pong frame has yet been sent in response. The application should send a Pong frame by calling SendPong as soon as possible.
topPingAutoRespond
void CkWebSocket_putPingAutoRespond(HCkWebSocket cHandle, BOOL newVal);
If TRUE, then a Pong frame is automatically sent when a Ping frame is received. If set to FALSE, then the application may check the NeedSendPong property to determine if a Pong response is needed, and if so, may call the SendPong method to send a Pong.
Note: If this property is TRUE, then the ReadFrame method will auto-consume incoming Ping frames. In other words, ReadFrame will continue with reading the next incoming frame (thus Ping frames will never be returned to the application). This relieves the application from having to worry about receiving and handling spurious Ping frames.
The default value is TRUE.
topPongAutoConsume
void CkWebSocket_putPongAutoConsume(HCkWebSocket cHandle, BOOL newVal);
If TRUE, then incoming Pong frames are automatically consumed, and a call to ReadFrame will continue reading until it receives a non-Pong frame. The PongConsumed property can be checked to see if the last ReadFrame method call auto-consumed a Pong frame.
The default value is TRUE.
topPongConsumed
Is TRUE if the last call to ReadFrame auto-consumed a Pong frame. This property is reset to FALSE each time a ReadFrame method is called, and will get set to TRUE if (1) the PongAutoConsume property is TRUE and (2) a Pong frame was consumed within the ReadFrame method.
The purpose of PongAutoConsume and PongConsumed is to eliminate the concern for unanticipated Pong frames in the stream. In the websocket protocol, both sides (client and server) may send Pong frames at any time. In addition, if a Ping frame is sent, the corresponding Pong response frame can arrive at some unanticipated point later in the conversation. It's also possible, if several Ping frames are sent, that a Pong response frame is only sent for the most recent Ping frame. The default behavior of Chilkat's WebSocket API is to auto-consume incoming Pong frames and set this property to TRUE. This allows the application to call a ReadFrame method for whatever application data frame it may be expecting, without needing to be concerned if the next incoming frame is a Pong frame.
topReadFrameFailReason
If the ReadFrame method returns FALSE, this property holds the fail reason. It can have one of the following values:
0 - No failure. 1 - Read Timeout. 2 - Aborted by Application Callback. 3 - Fatal Socket Error (Lost Connection). 4 - Received invalid WebSocket frame bytes. 99 - A catch-all for any unknown failure. (Should not ever occur. If it does, contact Chilkat.)top
UncommonOptions
const char *CkWebSocket_uncommonOptions(HCkWebSocket cHandle);
This is a catch-all property to be used for uncommon needs. This property defaults to the empty string and should typically remain empty. Can be set to a list of the following comma separated keywords:
- "ProtectFromVpn" - Introduced in v9.5.0.80. On Android systems, will bypass any VPN that may be installed or active.
Utf8
void CkWebSocket_putUtf8(HCkWebSocket cHandle, BOOL newVal);
When set to TRUE, all "const char *" arguments are interpreted as utf-8 strings. If set to FALSE (the default), then "const char *" arguments are interpreted as ANSI strings. Also, when set to TRUE, and Chilkat method returning a "const char *" is returning the utf-8 representation. If set to FALSE, all "const char *" return values are ANSI strings.
topVerboseLogging
void CkWebSocket_putVerboseLogging(HCkWebSocket cHandle, BOOL newVal);
If set to TRUE, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is FALSE. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.
topVersion
const char *CkWebSocket_version(HCkWebSocket cHandle);
Methods
AddClientHeaders
Adds the required WebSocket client-side open handshake headers. The headers specifically added to the previously specified REST object (in the call to UseConnection) are:
Upgrade: websocket Connection: Upgrade Sec-WebSocket-Key: ... Sec-WebSocket-Version: 13
Returns TRUE for success, FALSE for failure.
CloseConnection
Forcibly closes the underlying connection. This is a non-clean way to close the connection, but may be used if needed. The clean way to close a websocket is to send a Close frame, and then receive the Close response.
Returns TRUE for success, FALSE for failure.
topGetFrameData
const char *CkWebSocket_getFrameData(HCkWebSocket cHandle);
Returns the accumulated received frame data as a string. Calling GetFrameData clears the internal receive buffer.
Returns TRUE for success, FALSE for failure.
topGetFrameDataBd
Returns the accumulated received frame data in a BinData object. The received data is appended to the binData.
Calling this method clears the internal receive buffer.
GetFrameDataSb
Returns the accumulated received frame data in a StringBuilder object. The received data is appended to the sb.
Calling this method clears the internal receive buffer.
topLoadTaskCaller
PollDataAvailable
Check to see if data is available for reading on the websocket. Returns TRUE if data is waiting and FALSE if no data is waiting to be read.
topReadFrame
Reads a single frame from the connected websocket. If a frame was successfuly received, then the following properties are set: FrameOpcode, FrameDataLen, FinalFrame, and the received frame data can be retrieved by calling GetFrameData, GetFrameDataSb, or GetFrameDataBd.
Returns TRUE for success, FALSE for failure.
ReadFrameAsync (1)
Creates an asynchronous task to call the ReadFrame method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)
Returns NULL on failure
topSendClose
Sends a Close control frame. If includeStatus is TRUE, then the statusCode is sent in the application data part of the Close frame. A Close reason may be provided only if includeStatus is TRUE. If this Close was sent to satisfy an already-received Close frame, then the underlying connection will also automatically be closed.
Note: If a status code and reason are provided, the utf-8 representation of the reason string must be 123 bytes or less. Chilkat will automatically truncate the reason to 123 bytes if necessary. Also, the status code must be an integer in the range 0 to 16383.
The WebSocket protocol specifies some pre-defined status codes at WebSocket Status Codes. For a normal closure, a status code value of 1000 should be used. The reason can be any string, as long as it is 123 bytes or less.
Returns TRUE for success, FALSE for failure.
topSendCloseAsync (1)
Creates an asynchronous task to call the SendClose method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)
Returns NULL on failure
topSendFrame
Sends a single data frame containing a string. If this is the final frame in a message, then finalFrame should be set to TRUE. Otherwise set finalFrame equal to FALSE.
Returns TRUE for success, FALSE for failure.
SendFrameAsync (1)
Creates an asynchronous task to call the SendFrame method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)
Returns NULL on failure
topSendFrameBd
Sends a single data frame containing binary data (the contents of bdToSend). If this is the final frame in a message, then finalFrame should be set to TRUE. Otherwise set finalFrame equal to FALSE.
Returns TRUE for success, FALSE for failure.
SendFrameBdAsync (1)
Creates an asynchronous task to call the SendFrameBd method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)
Returns NULL on failure
topSendFrameSb
Sends a single data frame containing a string (the contents of sbToSend). If this is the final frame in a message, then finalFrame should be set to TRUE. Otherwise set finalFrame equal to FALSE.
Returns TRUE for success, FALSE for failure.
topSendFrameSbAsync (1)
Creates an asynchronous task to call the SendFrameSb method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)
Returns NULL on failure
topSendPing
Sends a Ping control frame, optionally including text data. If pingData is non-empty, the utf-8 representation of the string must be 125 bytes or less. Chilkat will automatically truncate the pingData to 125 bytes if necessary.
Returns TRUE for success, FALSE for failure.
SendPingAsync (1)
Creates an asynchronous task to call the SendPing method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)
Returns NULL on failure
topSendPong
Sends a Pong control frame. If this Pong frame is sent to satisfy an unresponded-to Ping frame, then the previously received Ping data is automatically sent in this Pong frame.
Returns TRUE for success, FALSE for failure.
topSendPongAsync (1)
Creates an asynchronous task to call the SendPong method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)
Returns NULL on failure
topUseConnection
Initializes the connection for a WebSocket session. All WebSocket sessions begin with a call to UseConnection. A Chilkat REST object is used for the connection because the WebSocket handshake begins with an HTTP GET request. The Chilkat REST API provides the ability to add custom headers, authentication, etc. to the opening GET handshake. It also provides the ability to establish connections over TLS or SSH and to benefit from the rich set of features already present relating to HTTP proxies, SOCKS proxies, bandwidth throttling, IPv6, socket options, etc.
Returns TRUE for success, FALSE for failure.
ValidateServerHandshake
Called after sending the opening handshake from the Rest object. Validates the server's response to the opening handshake message. If validation is successful, the application may begin sending and receiving data and control frames.
Returns TRUE for success, FALSE for failure.