qt程序运行时的错误error：undefined reference to `

出现的错误： 　　undefined reference to `_imp___ZN10QTcpSocketD1Ev' 　　undefined reference to `_imp___ZN10QTcpSocketC1EP7QObject' 　　undefined reference to `_imp___ZN10QTcpSocketD1Ev' 　　undefined reference to `_imp___ZN10QTcpSocketD1Ev' 　　undefined reference to `_imp___ZN10QTcpSocketD1Ev' 　　undefined reference to `_imp___ZN10QTcpSocketD1Ev' 　　undefined reference to `_imp___ZN10QTcpSocketD1Ev' 　　undefined reference to `_imp___ZN15QAbstractSocket13connectToHostERK7QStringt6QFlagsIN9QIODevice12OpenModeFlagEE' 　　undefined reference to `_imp___ZN15QAbstractSocket5closeEv' 　　collect2: ld returned 1 exit status 解决方法： 链接错误，检查.pro文件中是否缺少 　　 QT += network