Must include not only h files but cpp files when load a DLL using QPluginLoader

[d_stranz]

class ltcpOS : public QObject,tcpPluginInterface

class ltcpOS : public QObject,tcpPluginInterface

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I'm not sure I am remembering my C++ correctly, but I believe that this declaration is the same as:

class ltcpOS : public QObject, private tcpPluginInterface

class ltcpOS : public QObject, private tcpPluginInterface

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which you definitely do not want. It should be declared as:

class ltcpOS : public QObject, public tcpPluginInterface

class ltcpOS : public QObject, public tcpPluginInterface

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and you need to do the other things Wysota said.