Eu uso uma ferramenta de linha de comando chamada aria2 e ela faz o que você está descrevendo.
Features
Multi-connection Download aria2 can download a file from multiple sources/protocols and tries to utilize your maximum download bandwidth. Really speeds up your download experience. Lightweight aria2 doesn't require much memory and CPU time. The physical memory usage is typically 4MiB (normal HTTP/FTP downloads) to 9MiB (BitTorrent downloads). CPU usage in BitTorrent with download speed of 2.8MiB/sec is around 6%. Fully featured BitTorrent Client All features you want in BitTorrent client are available: DHT, PEX, Encryption, Magnet URI, Web-Seeding, Selective Downloads and Local Peer Discovery. Metalink Enabled aria2 supports The Metalink Download Description Format(aka Metalink v4). Old Metalink v3 is also supported. Metalink offers File verification, HTTP/FTP/BitTorrent integration and Configuration for language, location, OS, etc.