The following is a demonstration of the tcpstat.d script,
Here we run tcpstat.d as a large file is downloaded,
TCP_out TCP_outRe TCP_in TCP_inDup TCP_inUn
0 0 0 0 0
20 0 1540 0 0
632 0 576 0 0
560 0 115552 0 0
1872 0 2900480 0 0
1968 0 3032320 0 0
1776 0 2752160 0 0
752 0 999824 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
^C
We can see the TCP_in value rise to around 3 Mb/sec as the download occurs.