Multi-tcp is a project mainly written in Ruby, it's free.
Faster file transfers using multiple TCP connections
This was hacked together in 2 hours after getting frustrated by the time it took to transfer a 1.4 GB file over a single connection from the east coast to the West. A single TCP connection gives you only your fair share of the bottleneck link(s), and the large bw-delay product for cross-country connections means that congestion will completely shatter the existing window and will take several RTTs to be built up again.
This program logically breaks up the file you want to transfer into a number of specified chunks and sends each over a separate TCP connection. So, assuming there were n other TCP connections on the congested link and you create m connections, you will now get m/(n+m) share of the link where you previously only had 1/(n+1). Too high a value of m can cause a congestion collapse, so play around with the setting to figure out the best overall throughput.
The code is just about usable, and there's a ton of things to be done to make it work better, but who has the time?
Run server.rb at one end
Run client.rb at other end