URLFetchAsynchronous

URLFetchAsynchronous["url", eventFunction]
performs a connection in the background, calling the eventFunction when an event is raised.

Details and OptionsDetails and Options

  • Types of events that may be raised:
  • "data"returns a list of bytes and indicates that the connection has completed
    "progress"returns information about the current connect of the form
    "error"indicates that an error occurred while attempting to connect to a URL
    "headers"headers received from the web server
    "cookies"a list of all known cookies
    "statuscode"the status code returned by the server
  • The following options can be given:
  • "Method""GET"method used when connecting to an HTTP server
    "Parameters"{}parameters to be sent to the HTTP server
    "VerifyPeer"Trueverify the authenticity of a remote server using SSL certificates
    "Username"""connect to an HTTP server with a certain username
    "Password"""connect to an HTTP server with a certain password
    "UserAgent"Automaticchange the user agent sent to an HTTP server
    "Cookies"Automaticcookie management, Automatic, or may be handled manually by passing a list of cookies
    "StoreCookies"Trueif True, cookies will be stored in a global cookie share
    "Headers"{}headers to be manually sent to the HTTP server
    "BodyData"""contents of message body to be sent to the server
    "MultipartData"{}to upload multipart data, each part must be of the form , where {bytes} is a list of bytes
    "Progress"Falseif True, event will be raised
    "Transfer"Automaticif Automatic, the event returns once, and returns all the data downloaded; if , the event is raised multiple times with the data downloaded since the last event was raised
    "UserData"Noneany expression passed to this option will be stored for use of the AsynchronousTaskObject inside the event function; the data can be found by checking the options of AsynchronousTaskObject passed to the event function
    "ReadTimeout"0the maximum allowed time in seconds to download or upload data to the server
    "ConnectTimeout"0the maximum allowed time in seconds to connect to the server
  • When an event is raised, the event function passed to URLFetchAsynchronous will be executed. The event functions will be passed three arguments, the AsynchronousTaskObject, the event name, and the data received from the event. Event functions are the only method for handling data received from URLFetchAsynchronous.

ExamplesExamplesopen allclose all

Basic Examples (3)Basic Examples (3)

This opens a dialog when the download has finished:

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Store headers and cookies:

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Use the status code and error event to determine the availability of URLs.

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