tcpdrop —
drop a TCP connection
  
    | tcpdrop | laddr lport
      faddr fport | 
The tcpdrop command drops the TCP connection specified
  by the local address laddr, port
  lport and the foreign address
  faddr, port fport. Addresses and
  ports can be specified by name or numeric value.
If a connection to httpd(8) is
  causing congestion on a network link, one can drop the TCP session in charge:
$ fstat | grep 'httpd.*internet.*<--'
www      httpd      21307    3* internet stream tcp \
	0xd1007ca8 192.168.5.41:80 <-- 192.168.5.1:26747
 
The following command will drop the connection:
# tcpdrop 192.168.5.41 80 192.168.5.1 26747