cURL is a command-line tool for transferring data using various protocols, native to Linux. There are binaries available for Microsoft Windows, however; you can download them from the Web, such as at cURL's website (scroll to the bottom for Windows distributions, select a zip or 7zip download, unzip it to your machine, and open a command line in the bin or src directories):
Replace USERNAME and PASSWORD by your Windows username and password. The user must be in the "QlikView Administrators" group on the QlikView Server where the Management service is running. Be sure to also use the correct address of your server.
The service key generated with this call is valid for 1 minute.
Once this is done, you can use the service key to run a command through the QMS API.
8840332e-5776-4c52-9ae5-e913f75530c7 is the task ID for the task you want to abort. You can find this information in the QMC under Status > Tasks, and then clicking "Show Task Details" and selecting the "Log" tab.
Included is a zip file for QV12 containing a text file of request examples, and several XML body file examples. Make sure to replace USERNAME:PASSWORD, YOURQLIKSERVER, SERVICE_KEY_RESULT, and YOUR_TASK_ID with the appropriate information.