CONTROL
- Introduction to CTRL
- CONTROL Classes
- Types of Control Functions
- CONTROL graphics
- CONTROL Functions
  - Funtions A
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  - Functions E
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  - Functions W
    - waitThread()
      Waits for the end of the specified thread.
    - webSocketClose()
      The function closes the given WebSocket connection. The WebSocket number is the return value of webSocketOpen().
    - webSocketOpen()
      Opens a WebSocket connection to the given url.
    - webSocketRead()
      Tries to retrieve the next message form the WebSocket.
    - webSocketWrite()
      Writes data to the given WebSocket.
    - weekDay()
      Returns the weekday of a time.
    - wf_bottomBar_reload()
      Updates the buttons of the bottomBar of the wizard framework.
    - windowStyle()
      The function windowStyle() can be used to deactivate the control menu or only the minimize box
    - writeAuditBatchEntry()
      The function is used e.g. in production processes and it writes the batch id, the data point element the executed action had an influence on, the data point type, the executed action and the reason why the action was executed.
    - writeAuditEntry()
      The function writeAuditEntry is used to write set point values into the Audit trail panel.
    - writeDictionary()
      Writes the internal translation table to a file.
    - wss_getGenericSetting()
      Reads all workstation settings without hierarchy.
    - wss_getSpecificSetting()
      Reads a specific workstation setting without hierarchy.
    - wss_getSpecificWorkstationSetting()
      Reads a specific workstation setting with hierarchy.
    - wss_getWorkstationSettings()
      Reads all workstation settings with hierarchy.
  - Functions X
  - Functions Y
  - Functions Z
- CTRL Debugger
  With the CTRL Debugger you can debug the programming language Control.

webSocketWrite()

Writes data to the given WebSocket.

Synopsis

int webSocketWrite(int socket, string|blob data)

Parameters


Parameter	Description
socket	The number of the WebSocket the data is written to.
data	The data which is written to the WebSocket.

Return value

On success the function returns the number of bytes written and -1 on error.

Errors

Errors can be an illegal number of arguments or a wrong socket number.

Description

The function writes data onto the given WebSocket. For this process consider the following:

Especially on Linux and with SSL enabled, it is possible that the send buffer overflows when too much data is written to the WebSocket without interruption. The limit when this happens is depending on OS defaults and configuration.
It is therefore recommended to implement some kind of confirmation or handshake between client and server.
If this is not possible, it is important that sending from the client is interrupted (e. g. with delay()) before the buffer overflows.

To support this, the websocket will automatically be flushed if more than 64kB are buffered for it. If this fails, webSocketWrite() will return an error (-1). After such an error, getLastError() will contain an error with code ErrCode::UNEXPECTEDSTATE. Example code for handling this error:

int writeToWebSocket(int socket, string data)
{
  for (int i = 1; i <= 5; i++)
  {
    int written = webSocketWrite(socket, data);
    if ( written >= 0 )
      return written;  // success

    dyn_errClass err = getLastError();
    if ( getErrorCode(err) != (int)ErrCode::UNEXPECTEDSTATE )
      return written;  // error different from send buffer full

    // send buffer is full, use delay to allow socket to process data,
    // then try again
    delay(0, 10);
  }

  return -1;
}

Assignment

WebSocket functions

Availability

CTRL