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[SOLVED] Trying to get Ntp client to work

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  • SGaistS SGaist

    Hi,

    From what I can see you are trying to use the NTP reserved port (123), so you must have the credentials to do so. User available ports start at 1024

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    koahnig
    wrote on last edited by
    #3

    @SGaist
    Thanks for reply.

    123 was the only definite port number I could find through Google.
    Just tried 1024, 1025 and 0 with the very same result.

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    • M Offline
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      mcosta
      wrote on last edited by
      #4

      Hi.

      can we see how you open the socket?? which parameters?

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      • M mcosta

        Hi.

        can we see how you open the socket?? which parameters?

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        koahnig
        wrote on last edited by
        #5

        @mcosta
        Here is a link to the trial program..
        I basically changed the orginal project files for having an application and did some basic changes.
        Recently I have used the default constructor which does use only default parameters. However, also using parameters did not help.

        I have no experience with UDP sockets so far, I wonder if I do something very basic wrong.

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        • K Offline
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          koahnig
          wrote on last edited by
          #6

          Finally solved.

          Stupid user error or misleading Qt doc. Whereever you want to blame this.

          QHostAddress is only valid for IP addresses. However, since no IP addresses are typically given for NTP servers, I had used names found in internet. RTFM carefully helps.

          Well, I did not see a point to check out QHostAddress carefully, because with QTcpSockets I am using a mix of host names and ip addresses without caring. The parameter list of connectToHost has also QHostAddress. However, the other method contains QString as parameter. After years of using successfully there was no reason ....

          QHostInfo has to be involved for resolving the lookup.

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          • SGaistS SGaist

            Hi,

            From what I can see you are trying to use the NTP reserved port (123), so you must have the credentials to do so. User available ports start at 1024

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            koahnig
            wrote on last edited by koahnig
            #7

            @SGaist @mcosta
            123 is possible to use. See also above

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            • SGaistS Offline
              SGaistS Offline
              SGaist
              Lifetime Qt Champion
              wrote on last edited by
              #8

              If I understand you correctly, the behavior of QHostAddress changed between two versions of Qt ?

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              • SGaistS SGaist

                If I understand you correctly, the behavior of QHostAddress changed between two versions of Qt ?

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                koahnig
                wrote on last edited by
                #9

                @SGaist
                I am not sure about this. Also I am not sure when QHostAddress has been implemented first.

                Those prototype are available in QAbstractSocket

                connectToHost(const QString &, quint16, OpenMode, NetworkLayerProtocol);
                connectToHost(const QHostAddress &, quint16, OpenMode);
                

                I have started to use QTcpSocket in 2007 and I am using the same mechanism with host names and IP addresses. Being careful, it is obvious that I am using the first prototype. I have seen also the second prototype many times.
                When seeing the prototype using the ntp class, it was completely clear to me that the behaviour is identical to the behaviour of QTcpSocket. The "minor detail" of QHostAddress was overlooked. I saw no warning or anything. Therefore, I did not pay attention and looked in other areas where I did not have experience with.

                Finally I thought that I missed the obvious and started this thread. Unfortunately, I missed to add the section with the creation of the QHostAddress object by using the contructor QHostAddress::QHostAddress(const QString & address) with a host name.
                That would have given others the chance to point out my stupid mistake.

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                • SGaistS Offline
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                  SGaist
                  Lifetime Qt Champion
                  wrote on last edited by
                  #10

                  QHostAddress dates back to Qt 3 so it's a pretty old class

                  So if I follow you correctly, you thought you were using the first one, while in practice the second one was called ?

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                  • SGaistS SGaist

                    QHostAddress dates back to Qt 3 so it's a pretty old class

                    So if I follow you correctly, you thought you were using the first one, while in practice the second one was called ?

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                    koahnig
                    wrote on last edited by
                    #11

                    @SGaist
                    Basically yes. Simply running into the trap and did not pay attention.

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                    • SGaistS Offline
                      SGaistS Offline
                      SGaist
                      Lifetime Qt Champion
                      wrote on last edited by
                      #12

                      I'm surprised that it does an automatic conversion like that...

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                      • SGaistS SGaist

                        I'm surprised that it does an automatic conversion like that...

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                        koahnig
                        wrote on last edited by koahnig
                        #13

                        @SGaist said:

                        I'm surprised that it does an automatic conversion like that...

                        Just try HostAddress.pro

                        QT       += core network
                        QT       -= gui
                        TARGET = HostAddress
                        CONFIG   += console
                        CONFIG   -= app_bundle
                        TEMPLATE = app
                        SOURCES += main.cpp
                        

                        main.cpp:

                        #include <QCoreApplication>
                        #include <QHostAddress>
                        
                        int main(int argc, char *argv[])
                        {
                            QCoreApplication a(argc, argv);
                        
                            QHostAddress hadd ( "any.domain.com" );
                        
                            return a.exec();
                        }
                        

                        This does not tell you a thing. Clearly by reading the docs that is wrong and you have to look up the ip address and use a proper ip address.
                        However, the constructor does notice that the input is wrong. I would expect to see at least a message. Probably the reason is that the class is rooting back to Qt3.

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                        • SGaistS Offline
                          SGaistS Offline
                          SGaist
                          Lifetime Qt Champion
                          wrote on last edited by
                          #14

                          Hi,

                          In fact the constructor taking a string doesn't detect anything particular. However using setAddress would return false so it might be a better option currently

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                          • SGaistS SGaist

                            Hi,

                            In fact the constructor taking a string doesn't detect anything particular. However using setAddress would return false so it might be a better option currently

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                            koahnig
                            wrote on last edited by
                            #15

                            @SGaist
                            You are right. Also when reading all the details in the documentation it becomes obvious.

                            My point is that this is not really consistent with error reporting in other sections of Qt. In my opinion Qt's beauty is because of the error reporting, which helps to avoid problems. For instance when using a non-existing signal in a connect or the parameters are not fitting one receives a message reporting the problem. Certainly when one is not checking the connect's return value, the information might be lost. However, when you start to check the return value with an assert it is very powerful and you see immediately your problem.

                            For consistency I would expect to obtain at least a direct warning, when a non-IP address is handed over. Compared to other really good things in Qt, this is rather sloppy and forms a trap.

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                            • SGaistS Offline
                              SGaistS Offline
                              SGaist
                              Lifetime Qt Champion
                              wrote on last edited by
                              #16

                              Just talked with one the network kings: you should use isNull before using your QHostAddress object, then you'll know for sure that you have a valid address.

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                              • SGaistS SGaist

                                Just talked with one the network kings: you should use isNull before using your QHostAddress object, then you'll know for sure that you have a valid address.

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                                koahnig
                                wrote on last edited by
                                #17

                                @SGaist

                                Thanks for following up. Certainly I will take care this next time. I guess I will remember.

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