I am using Qt’s QTcpSocket class to create a small chat client/server application. When I compile my code, the compiler returns the following error:

main.cpp:3:22: fatal error: QTcpSocket: No such file or directory

This refers to #include .

Where is this library located and how can I install it?

After google it, we just need to add

QT += network

in the .pro file which is generated by

qmake -project

. Otherwise the module in which those headers are defined/libraries are built won’t be loaded.

NOTICE: If you use qmake -project after you modified .pro file, you will still get the above error. Because using qmake -project will change the .pro file back to before!

The commands I used is described in my article:

qmake -project qmake -tp vc

The problem described above is solved. Just keep in mind that qmake -project is used to generate .pro file and qmake -tp vc is used to generate Visual Studio project file.