I read the source code and found the problem might be a single thread is responsible for reading data from file and then write data into the socket buffer. I tried to modify it by myself, but I’m not familiar with C++ and Qt, so I only increased the 10000-byte const in void Dukto:sendData(qint64 b) to 320000. And I also enabled Jumbo-frame feature in my network card. This way, I can increase the speed to 100MB/s. My approach is not elegant, but there is still room for improvement. I hope you can make dukto faster.