A request XML packet starting, stopping or restarting server services contains the srv_man operation node:
<packet version="1.4.2.0">
<server>
<srv_man>
...
</srv_man>
</server>
</packet>
The srv_man node is presented by complex type ServicesManagementType (server_input.xsd) and structured as follows:

plesk_server.xsd).plesk_server.xsd). Allowed values: start | stop | restart.