Couple of ways:
1) Create a method in the webservice which can be used to poll the health of webservice.
2) I am not sure of how your webserices are built, but obtain the wsdl file by typing in the required url in the browser. For example to obtain wsdl file from weblogic you can type
http://myServer:port/MyProject/MyWebService.jws?WSDL
3) If have a UDDI registry being used then I think you can inquire about a webservice.