What is the format of the image on server side ? Previously you tried
GL_RGB
data format to bind a texture, but later you tried QImage::format_RGB32 too. So which one is it ? How many bytes per pixel ? What data order (bgr or rgb, row major or column major) ?
Btw. what is the bytes.size() ? In case of 800x600 24 bit rgb image data, size should be 1 440 000 bytes.