TTCP is used to test TCP throughput. The Chesapeake version is based on Java. The sources for the C and Java version are available on the Netcordia web site www.netcordia.com/resources/tools. There are Windows versions of ttcp by other organizations, which you can find through Google.
In addition to TTCP, there are other useful tools, networking tech tips, recorded presentations, and white papers available on the Netcordia Resources web page.
The files are:
README - installation and running directions.
ttcp.zip - a zip file containing the distribution files.
ttcp.tar - a tar file containing the distribution files.