So, I have deployed NetXMS WebAPI with Tomcat 9 instead of Jetty and it doesn't work even with http.
I have attached the Catalina log and also Wireshark traces.
Tried this with Tomcat 7 and 9.

What am I doing wrong?

The bellow error is showed :
23-Mar-2018 09:49:52.812 SEVERE [http-nio-9080-exec-12] org.restlet.resource.ServerResource.doCatch Exception or error caught in server resource
 org.restlet.resource.ResourceException: Internal Server Error (500) - The server encountered an unexpected condition which prevented it from fulfilling the request
    at org.restlet.resource.ServerResource.doHandle(ServerResource.java:527)
    at org.restlet.resource.ServerResource.post(ServerResource.java:1341)
    at org.restlet.resource.ServerResource.doHandle(ServerResource.java:606)
    at org.restlet.resource.ServerResource.doNegotiatedHandle(ServerResource.java:662)
    at org.restlet.resource.ServerResource.doConditionalHandle(ServerResource.java:348)
    at org.restlet.resource.ServerResource.handle(ServerResource.java:1020)
    at org.restlet.resource.Finder.handle(Finder.java:236)
    at org.restlet.routing.Filter.doHandle(Filter.java:150)
    at org.restlet.routing.Filter.handle(Filter.java:197)
    at org.restlet.routing.Router.doHandle(Router.java:422)
    at org.restlet.routing.Router.handle(Router.java:641)
    at org.restlet.routing.Filter.doHandle(Filter.java:150)
    at org.restlet.routing.Filter.handle(Filter.java:197)
    at org.restlet.routing.Filter.doHandle(Filter.java:150)
    at org.restlet.routing.Filter.handle(Filter.java:197)
    at org.restlet.routing.Filter.doHandle(Filter.java:150)
    at org.restlet.routing.Filter.handle(Filter.java:197)
    at org.restlet.routing.Filter.doHandle(Filter.java:150)
    at org.restlet.engine.application.StatusFilter.doHandle(StatusFilter.java:140)
    at org.restlet.routing.Filter.handle(Filter.java:197)
    at org.restlet.routing.Filter.doHandle(Filter.java:150)
    at org.restlet.routing.Filter.handle(Filter.java:197)
    at org.restlet.engine.CompositeHelper.handle(CompositeHelper.java:202)
    at org.restlet.engine.application.ApplicationHelper.handle(ApplicationHelper.java:77)
    at org.restlet.Application.handle(Application.java:385)
    at org.restlet.routing.Filter.doHandle(Filter.java:150)
    at org.restlet.routing.Filter.handle(Filter.java:197)
    at org.restlet.routing.Router.doHandle(Router.java:422)
    at org.restlet.routing.Router.handle(Router.java:641)
    at org.restlet.routing.Filter.doHandle(Filter.java:150)
    at org.restlet.routing.Filter.handle(Filter.java:197)
    at org.restlet.routing.Router.doHandle(Router.java:422)
    at org.restlet.routing.Router.handle(Router.java:641)
    at org.restlet.routing.Filter.doHandle(Filter.java:150)
    at org.restlet.routing.Filter.handle(Filter.java:197)
    at org.restlet.engine.CompositeHelper.handle(CompositeHelper.java:202)
    at org.restlet.Component.handle(Component.java:408)
    at org.restlet.Server.handle(Server.java:507)
    at org.restlet.engine.connector.ServerHelper.handle(ServerHelper.java:63)
    at org.restlet.engine.adapter.HttpServerHelper.handle(HttpServerHelper.java:143)
    at org.restlet.ext.servlet.ServerServlet.service(ServerServlet.java:1117)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:494)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:651)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:407)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:754)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1376)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.net.ConnectException: Connection refused: connect
    at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
    at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:589)
    at org.netxms.client.NXCSession.connect(NXCSession.java:1805)
    at org.netxms.client.NXCSession.connect(NXCSession.java:1778)
    at org.netxms.websvc.handlers.AbstractHandler.login(AbstractHandler.java:375)
    at org.netxms.websvc.handlers.Sessions.onPost(Sessions.java:78)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.restlet.resource.ServerResource.doHandle(ServerResource.java:508)
    ... 63 more

23-Mar-2018 09:49:52.849 INFO [http-nio-9080-exec-12] org.restlet.engine.log.LogFilter.afterHandle 2018-03-23 09:49:52 10.2.56.130 status 10.3.57.29 9080 POST /webapi/sessions - 500 56 0 1206 http://10.3.57.29:9080 Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36 http://mydomain:8080/datasources/edit/12

Thank you,
Raoul

Thank you for your response.

I will follow the guide you provided.

Regards,
Raoul

If grafana is running in https mode, it will not accept datasources which are not from https url's.
The guide is a bit of a hack to get the API working with the same built in web server that comes with the windows WebUI installation. What I can suggest is to deploy a dedicated web server like Apache Tomcat and following this guide, configure it for SSL usage https://www.mulesoft.com/tcat/tomcat-ssl

Regards,
Eriks