1 2 Previous Next 29 Replies Latest reply on Jun 23, 2014 8:06 AM by user6753138 Go to original post
      • 15. Re: How much Java does one need to know?

        This morning I started the RasPi (the one that worked) and tried to connect to the Device Controler.

        I just get "connecting" then the "device not registered". I have treid about 6 times now including  a RaPi reboot

        The cd javame8ea/bin/

        ./usertest.sh starts OK and is in wait mode.


        Although yesterday it worked and I have made no changes.The is the only RasPI connected to my WLAN.


        There seem to be some inconsistency here  with running the Device controller and getting connected.

        Ping works and returns a time of 64mS


        Later I want to be able to programme java on 3 Raspberry Pis so I hope this issue cane be resolved.


        Can you please help me out?


        Many thanks



        • 16. Re: How much Java does one need to know?

          Hi Nigel,


          I'm assuming that you did not change the version of ME SDK on host and ME runtime on RPi. In this case the only thing I would suggest is to check that your jwc_properties.ini file on the RPi in javame8ea/bin is not corrupted. E.g. you can overwrite it with the original from the EA2 download package.

          Other than that I cannot imagine what could be wrong with Java to cause such problem..



          • 17. Re: How much Java does one need to know?

            I re-installe all the SW on the Raspberry Pi, OS and Java - now works.


            Just one last thing.

            Is this course going to be held at a later date?

            I've just been told that I will be in hospital 14th May for about 2 weks.

            I can take a laptop and connect it to the Hop. Internet  but no raspberry pi connections are tolerated.

            If there is not a course this year, I'll stay erolled and read all the course material and complete the assignments

            at a (much) later date. SUch is life.


            Many thanks for your patience and help



            • 18. Re: How much Java does one need to know?

              Hi Nigel -


              Yes - we are running the course again, the start date is now the 30th of May.


              See this link to enroll.



              • 19. Re: How much Java does one need to know?
                Colin Cooper

                Sorry to hear you're being hospitalised.


                One thing you might like to consider: leave the pi at home, but adjust your home router to expose the ssh port + any which are required by the AMS

                • 20. Re: How much Java does one need to know?

                  Hello Mr. Cooper,


                  Does that mean there are no more course repeats his year?



                  • 21. Re: How much Java does one need to know?

                    Hi Nigel


                    Tom (tmcginn) the course instructor said there will be another course taking place on the 30th of May (see the post above Mr Colin Cooper). Can you participate? There is also an enroll link provided by Tom here.


                    Mr Cooper gave you a suggestion on connecting to the RPi in case you will still be in hospital.


                    Good luck.

                    • 22. Re: How much Java does one need to know?

                      Hello Trintay,


                      the 30th May course is the one I am (or should be) enrolled on - I was wondering if there was another course later.


                      I  see I also make a Typo  that is the 22th May not the 14th of May  when I'm off.


                      adjust your home router to expose the ssh port + any which are required by the AMS.:

                      I do not know how to do this. I have always assumed that one would need a service like DynDns to generate a "service"  IP

                      and only then can I access the Raspberry pi outside my local network (192.1660.1.xxx) . I then would need to change the IP address to this Dyndns IP to get Internet connections. Please correct me if I am wrong.

                      • 23. Re: How much Java does one need to know?

                        Hi Nigel -


                        We moved the start date from the 19th of May to 30th of May to allow ourselves enough time to re-record some of the lessons due to changes between Early Access 2 and General Availability (GA) of the Java ME 8 software.


                        The second run of the MOOC will likely be our last for a little while.



                        • 24. Re: How much Java does one need to know?
                          Colin Cooper

                          Hi Nigel,


                          The important thing to remember is that you have two ip addresses of interest.  The local address of your pi, and the internet address of your router.  The trick is to get specific ports on you router forwarded to the pi.

                          Exactly how you achieve this will depend on which router you have.  Assuming you have admin access to it (normally though a web page), the initial steps would be roughly:

                          1. on pi: ensure you have ssh available on your pi - you're probably already using this?
                          2. on router: best if you can check that your pi has a static ip address -  there will be a page to set this.  This is just the address visible within your local network, and doesn't need to change.
                          3. on router: find a "port forwarding" or "external services" page on the router, and have it forward TCP port 22, or "ssh" to your pi's local name or address.

                          That makes it accessible to the internet -- but only if you know your router's IP address, which may change each reboot.


                          You can test it at this stage: first find out your router's external IP address -- many sites exist e.g. http://whatismyipaddress.com/


                          Now with a computer not connected to your network ssh to that ip:22 (e.g. with "putty" on windows, "ssh" on linux, or the invaluable "ConnectBot" on android)


                          Assuming this gets you to a login prompt, you're mostly there. 


                          As you say you need a dynamic dns account (DynDNS or the one I use: no-ip)

                          Set up a free account there, after choosing a suitable domain name.  The dns provider may have a client you can install on a home machine, but first check if your router has a page to enter your dns account details -- if it does, it will automatically tell the dns provider whenever your router's ip address changes.  If all else fails, the dynamic dns provider will have a page where you can manually enter the ip address.


                          Assuming that has worked, retry the remote ssh test, but this time connecting to your-dns-name:22


                          Now you have remote ssh access to your pi from anywhere :-)


                          For the purpose of this course, you'll additionally have to have your router forward any ports which the AMS needs (simply redo step 3 with the new port number(s)).  I don't know which ports these might be, but hopefully an instructor or javeme developer can tell us or point us at the relevant documentation.


                          Finally, some warnings:

                          • Your pi is now exposed to the world.  You should probably read the javame documentation and get rid of that NullAuthenticationProvider we're all been using.
                          • Make sure your pi has fail2ban installed. This will bar hackers after a few failed attempts to guess your password.
                            • (dpkg -l |grep fail2ban) || sudo apt-get install fail2ban
                          • Make sure your pi has a decent password!
                          • Back up the sdcard before you go into hospital, in case you do get hacked
                          • Good luck!
                          • 25. Re: How much Java does one need to know?



                            Yes, you can use DynDns, or No-IP so that you can make your home router accessible to the internet (using a home PC as the proxy). Then you need to set port forwarding in your router (consult your router manual) to the static ip address you assigned to your Pi. The downside to running a Pi remotely like this is you cannot physically interact with it for eg, testing the switch, lighting LEDs, attaching other sensor components required and so on.


                            However, since you say you are going to be in hospital for two weeks, you might make it back home in time for Lesson 2, where the fun starts with working with sensors. Although Lesson 1 has started, it really is introductory (setting up and get Pi running, learning multiple threading etc) and most likely you can still cope without having the Pi in the hospital (just test your homework on the emulator). You can review the notes for Lesson 1 now to get some understanding of what is required and play around with setting up the Rpi before your actual course date starts.


                            If I was you, just enroll and see how it goes, besides, the quiz deadline for a particular lesson is a week after its starts so it really is manageable.

                            • 26. Re: How much Java does one need to know?

                              Thank you for all that information.


                              I will be taking the course anyway. if I cannot do any homework , well -  I just do it later on my own. This means I can not  get the Cert, but I think

                              the course will be extremely helpful for me. I just do not want to miss it.


                              My MRI was on the 14th and the main day is the 22nd. So that's enough about that.


                              Thank  you for all your help.



                              • 27. Re: How much Java does one need to know?

                                Hello again,


                                Well I was able to do some work but due to further treatment nowhere near enough to get the certificate.


                                Two questions:

                                How long will the Lessons be available to me online?  When I leave  this hospital next week  I want to completly re-do the course

                                at home.I'll be too late for the quizes, but thats life. I did enjoy the course so far.


                                When is the next course?


                                T, too ,agree that slides would be a good idea. Perhaps also a pdf for each lesson salient points..



                                best regards

                                • 28. Re: How much Java does one need to know?

                                  Hello Nigel, hope you are feeling better!


                                  To answer your questions:


                                  1) I saw Tom mention a while ago that he plans to leave the latest course materials permanently available. So you should not have a problem accessing the materials, even after the course, especially if you registered for the May/June session. If you only registered for the first session, you need to let Tom know so he can give you access to the latest course materials.


                                  2) Tom did say there won't be another course for a while after the May/June session, but you never know. You can subscribe to the latest Oracle news feeds or visit their website regularly for any future Java embedded course offerings.


                                  Don't worry about the certificate, whats important is the knowledge and experience you gained from the course.


                                  Good luck!

                                  1 person found this helpful
                                  • 29. Re: How much Java does one need to know?

                                    Thank you ,and bye.



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