public with sharing class Invoke_Webservice {

    public void invokeService(){

         try{

            String username='email';
            String password='pass';
            HttpRequest req = new HttpRequest();
            req.setEndpoint('http://999.999.999.999:80/SFSAP');
            req.setMethod('GET');
            Blob headerValue = Blob.valueOf(username + ':' + password);
            String authorizationHeader = 'Basic '+
                   EncodingUtil.base64Encode(headerValue);
            req.setHeader('Authorization', authorizationHeader);
            req.setHeader('Content-Type', 'application/soap+xml');
            req.setTimeout(80000);

            //wsdl2apex class calling

            wwwApprouterComConnectorsWsdl.Provide_ServicePort test = new wwwApprouterComConnectorsWsdl.Provide_ServicePort();
            wwwApprouterComConnectorsResponse4.Product_element result;
            result = test.Provide_Service('OAOM-PUMP','Sample','100-200','HALB','M');
            System.debug(result);

            Http http = new Http();
            HttpResponse res = http.send(req);
            System.debug(res);
          }
           catch(Exception e){
           System.debug(e);
        }
    }

}