If you can access the file through a network share or mounted driver outside of Qt then you probably just use QFile directly

If the file exists on a machine that has a running FTP server or HTTP server, and the file is accessible to that FTP or HTTP server, then you could use QFtp or QNetworkAccessManager (not QHttp) to access that server and retrieve the file.
FTP (Chinese)
HTTP (Chinese)

If you can install and run a program of your own on the machine with the file then you can use QTcpSocket to create a server and client pair to transfer the file.

Try to work out which option applies.