FreeBSD uses FETCH command in order to download source codes or binary packages it needs to compile or install.If you are on slow connection like caf or shared band this process become painful. FETCH can't resume in most cases and fails so as the process trying to install or  compile something.  I want to know if it is possible to use aria2 or axel instead of fetch.
Change FreeBSD's fetch with aria2 or axel
freebsd
Check man ports:fetch   Fetch all of the files needed to build this port from the          sites listed in MASTER_SITES and PATCH_SITES.  See FETCH_CMD,          MASTER_SITE_OVERRIDE and MASTER_SITE_BACKUP.....FETCH_CMD    Command to use to fetch files.  Normally fetch(1).