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# WebSocket Callback Functions

The following callback APIs are called by the web_websocket functions. For a complete listing, see Miscellaneous Functions.

## onOpenCB

void onOpenCB(const char* connectionID, const char * AccumulatedHeadersStr, int AccumulatedHeadersLen)

ConnectionID | The connection ID.
AccumulatedHeadersStr | The accumulated header string.
AccumulatedHeadersLen | The length of the header string.

This callback is triggered when the WebSocket connection's readyState changes to OPEN. This indicates that the connection is ready.

## onMessageCB

void onMessageCB(const char* connectionID, int isbinary, char *data, int length)

ConnectionID | The connection ID.
isbinary | An indicator whether the string is binary or text.
Data | The buffer received from the server.
Data Length | The length of the buffer.

This callback is triggered when a message is received from the server.

## onCloseCB

void onCloseCB(const char* connectionID, int isClosedByClient, int code, const char* reason, int length)

ConnectionID | The connection ID.
isClosedByClient | An indicator whether the connection was closed by the client.
Code | A 4-digit close code.
Reason | A string indicating the reason of the closure.
Length | The length of the reason message (0 for NULL).

This callback is triggered when the connection to the server is closed.

## onErrorCB

void onErrorCB(const char* connectionID, const char * message, int length)

ConnectionID | The connection ID.
Message | The message of the error event (may be NULL).
Length | The length of the error message (0 for NULL).

This callback is triggered when an error is received from the server.

## Examples

#### Example - OnOpenCB

Copy code

    void OnOpenCB0 (const char* connectionID,
    const char * AccumulatedHeadersStr,
    int AccumulatedHeadersLen)
    {
    // lr_output_message("WebSocket ID = %s connected", connectionID);
    // lr_save_param_regexp (AccumulatedHeadersStr,
    //              AccumulatedHeadersLen,
    //              "RegExp=Sec-WebSocket-Accept: (.+)\\r\\n",
    //              "ResultParam=Accept",
    //               LAST);
    // lr_output_message("Sec-WebSocket-Accept = [%s]",
    // lr_eval_string("{Accept}"));
    }

#### Example - OnMessageCB

Copy code

    void OnMessageCB0 (const char* connectionID,
    int isbinary,
    const char * data,
    int length)
    {
    //if (isbinary) {
    //lr_output_message("WebSocket ID = %s. [%d] bytes binary message received.", connectionID, length);
    //}
    //else {
    //lr_output_message("WebSocket ID = %s. [%d] bytes text message received.", connectionID, length);
    //}
    }

#### Example - OnErrorCB

Copy code

    void OnErrorCB0 (const char* connectionID,
    const char * message,
    int length)
    {
    //lr_output_message("WebSocket ID = %s error occurred. Error message = %s", connectionID, message);
    }

#### Example - OnCloseCB

Copy code

    void OnCloseCB0 (const char* connectionID,
    int isClosedByClient,
    int code,
    const char* reason,
    int length)
    {
    //lr_output_message("WebSocket ID = %s closed. CloseCode= %d, CloseReason=%s", connectionID, code, reason);
    }

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